Search

We studied mean changes in birthweight from the first to the second delivery according to length of the inter-pregnancy interval. We also studied recurrence risk of low birthweight, preterm birth and perinatal death. We followed all women in Norway from their first to their second singleton delivery at gestational week 22 or beyond during the years 1970-2019, a total of 654 100 women. Data were obtained from the Medical Birth Registry of Norway. Mean birthweight increased from the first to the second delivery, and the increase was highest in pregnancies conceived < 6 months after the first delivery; adjusted mean birthweight increase 227 g (g) (95% CI; 219-236 g), 90 g higher than in pregnancies conceived 6-11 months after the first delivery (137 g (95% CI; 130-144 g)). After exclusion of women with a first stillbirth, the mean increase in birthweight at inter-pregnancy interval < 6 months was attenuated (152 g, 95% CI; 143-160 g), but remained higher than at longer inter-pregnancy intervals. This finding was particularly prominent in women > 35 years (218 g, 95% CI; 139 -298 g). In women with a first live born infant weighing < 2500 g, mean birthweight increased by around 1000 g to the second delivery, and the increase was most prominent at < 6 months inter-pregnancy interval. We found increased recurrence risk of preterm birth at inter-pregnancy interval < 6 months, but no increased recurrence risk of low birthweight, small for gestational age infant or perinatal death. In conclusion, we found the highest mean increase in birthweight when the inter-pregnancy interval was short. Our results do not generally discourage short pregnancy intervals., (© 2024. The Author(s).)

To describe trends in low birth weight (less than 2, 500 g), the authors analyzed 1.7 million live births and stillbirths registered between 1967 and 1995 in the Medical Birth Registry of Norway. The proportion of low birth weight infants declined from 5.3% in 1967 to 4.5% in 1979 and was followed by a steady increase that reached 5.3% in 1995. Similar trends were observed in the proportion of preterm births. Mean birth weight increased from 3, 456 g in 1967 to 3, 518 g in 1995. From 1979 to 1987, the increase in the prevalence of low birth weight was related to single births, and after 1987 it was related to multiple births, which increased from 2.3% of all births in 1987 to 3.1% in 1995. The proportion of low birth weight in births occurring after 37 weeks of gestation declined continuously, resulting in low birth weight births' to an increasing extent being made up of births occurring before 37 weeks of gestation. In an ecologic analysis based on county of maternal residence, the increase in low birth weight among single births was accounted for by an increase in deliveries with induction of labor or cesarean section. The authors conclude that the overall proportion of low birth weight births is not a good indicator of health in a population with extensive use of obstetric procedures that affect gestational age or assisted fertilization, which increases the number of multiple births. Am J Epidemiol 1999; 149: 1128–33. [ABSTRACT FROM PUBLISHER]

Background: A previous randomized dietary intervention in pregnant women from the 1970s, the Harlem Trial, reported retarded fetal growth and excesses of very early preterm births and neonatal deaths among those receiving high-protein supplementation. Due to ethical challenges, these findings have not been addressed in intervention settings. Exploring these findings in an observational setting requires large statistical power due to the low prevalence of these outcomes. The aim of this study was to investigate if the findings on high protein intake could be replicated in an observational setting by combining data from two large birth cohorts., Methods: Individual participant data on singleton pregnancies from the Danish National Birth Cohort (DNBC) ( n = 60,141) and the Norwegian Mother, Father and Child Cohort Study (MoBa) ( n = 66,302) were merged after a thorough harmonization process. Diet was recorded in mid-pregnancy and information on birth outcomes was extracted from national birth registries., Results: The prevalence of preterm delivery, low birth weight and fetal and neonatal deaths was 4.77%, 2.93%, 0.28% and 0.17%, respectively. Mean protein intake (standard deviation) was 89 g/day (23). Overall high protein intake (>100 g/day) was neither associated with low birth weight nor fetal or neonatal death. Mean birth weight was essentially unchanged at high protein intakes. A modest increased risk of preterm delivery [odds ratio (OR): 1.10 (95% confidence interval (CI): 1.01, 1.19)] was observed for high (>100 g/day) compared to moderate protein intake (80-90 g/day). This estimate was driven by late preterm deliveries (weeks 34 to <37) and greater risk was not observed at more extreme intakes. Very low (<60 g/day) compared to moderate protein intake was associated with higher risk of having low-birth weight infants [OR: 1.59 (95%CI: 1.25, 2.03)]., Conclusions: High protein intake was weakly associated with preterm delivery. Contrary to the results from the Harlem Trial, no indications of deleterious effects on fetal growth or perinatal mortality were observed.

Background: Low birth weight (LBW) is associated with a higher risk of end-stage renal disease (ESRD). The relative impacts of absolute birth weight, birth weight in relation to gestational age and preterm birth are, however, uncertain., Methods: The Medical Birth Registry of Norway has since 1967 recorded data on all births. All patients with ESRD since 1980 have been registered in the Norwegian Renal Registry. Data from these registries were linked. All individuals registered in the Medical Birth Registry were included and the development of ESRD was used as endpoint in Cox regression statistics. LBW and LBW for gestational age [small for gestational age (SGA)] according to the 10th percentiles were used as the main predictor variables., Results: Of the 2 679 967 included subjects, 1181 developed ESRD. Compared with subjects without LBW, subjects with LBW had an adjusted hazard ratio (aHR) for ESRD of 1.61 (1.38-1.98). SGA had an aHR of 1.44 (1.22- 1.70). Further analyses showed that as compared with subjects who had none of the risk factors LBW, SGA and preterm birth, subjects with one risk factor had an aHR of 1.05 (0.84-1.31), subjects with two risk factors had an aHR of 1.67 (1.40-1.98) and subjects with three risk factors had an aHR of 2.96 (1.84-4.76)., Conclusions: We conclude that LBW was associated with increased risk for ESRD during the first 50 years. Our analyses add to previous knowledge showing that only subjects with at least two of the risk factors LBW, SGA or preterm birth have increased risk., (© The Author(s) 2020. Published by Oxford University Press on behalf of ERA-EDTA.)

Background: Adverse birth outcomes are more frequent among mothers with inflammatory bowel diseases (IBDs) than non-IBD mothers. In recent studies, air pollution, such as high concentrations of nitrogen dioxide (NO 2 ), is reckoned as a risk factor for preterm birth in the general population. In this study, we investigated whether IBD mothers are at higher risk of preterm birth when exposed to NO 2 compared to non-IBD mothers. Methods: We used information from the Norwegian Mother, Father and Child Cohort Study (MoBa). The pregnancy cohort was linked to the Norwegian Medical Birth Registry and air-pollution exposure data available from a subset of the study cohort. The relevant outcome in this study was preterm birth. A total of 16,170 non-IBD and 92 IBD mothers were included in the study. Results: The mean exposure of NO 2 during the pregnancy was similar for IBD and non-IBD mothers, 13.7 (6.9) μg/m 3 and 13.6 (4.2) μg/m 3 , respectively.IBD mothers with higher exposure of NO 2 in the second and third trimester were at significant risk of preterm birth compared to non-IBD mothers [OR = 1.28 (CI 95%: 1.04-1.59) and OR = 1.23 (95% CI: 1.06-1.43), respectively]. The mean NO 2 exposure was significantly higher in IBD mothers with preterm birth than in IBD mothers who delivered at term, at 19.58 (1.57) μg/m 3 and 12.89 (6.37) μg/m 3 , respectively. Conclusions: NO 2 exposure influenced the risk of preterm birth in IBD mothers. Higher risk of preterm birth in IBD was associated with higher exposure of NO 2 , suggesting vulnerability of preterm birth in IBD when exposed to NO 2 .

Background: Maternal caffeine intake has repeatedly been linked to babies being born small for gestational age (SGA). SGA babies are known to be at increased risk for adverse neonatal outcomes. The aim of this study was to explore the associations between prenatal caffeine exposure and neonatal health., Methods: The study is based on 67,569 full-term singleton mother-infant pairs from the Norwegian Mother and Child Cohort Study. Caffeine consumption from different sources was self-reported in gestational week 22. Neonatal compound outcomes, namely (1) morbidity/mortality and (2) neonatal intervention, were created based on the Medical Birth Registry of Norway. Adjusted logistic regression was performed., Results: Caffeine exposure was associated to SGA (OR = 1.16, 95%CI: 1.10; 1.23) and being born SGA was significantly associated with neonatal health (OR = 3.09, 95%CI: 2.54; 3.78 for morbidity/mortality; OR = 3.94, 95%CI: 3.50; 4.45 for intervention). However, prenatal caffeine exposure was neither associated with neonatal morbidity/mortality (OR = 1.01, 95%CI: 0.96; 1.07) nor neonatal intervention (OR = 1.02, 95%CI: 1.00; 1.05 for a 100 mg caffeine intake increase). Results did not change after additional adjustment for SGA status., Conclusions: Moderate prenatal caffeine exposure (< 200 mg/day) does not seem to impair neonatal health, although prenatal caffeine exposure is associated with the child being born SGA and SGA with neonatal health. We suggest diversity in neonatal outcomes of SGA infants according to the underlying cause of low birth weight.

Background: Previous studies have demonstrated that low birth weight (LBW) is associated with higher risk for end-stage renal disease (ESRD). However, both LBW and ESRD cluster in families. The present study investigates whether familial factors explain the association between LBW and ESRD., Study Design: Retrospective registry-based cohort study., Setting & Participants: Since 1967, the Medical Birth Registry of Norway has recorded medical data for all births in the country. Sibling data are available through the Norwegian Population Registry. Since 1980, all patients with ESRD in Norway have been registered in the Norwegian Renal Registry. Individuals registered in the Medical Birth Registry with at least 1 registered sibling were included., Predictor: LBW in the participant and/or LBW in at least 1 sibling., Outcome: ESRD., Results: Of 1,852,080 included individuals, 527 developed ESRD. Compared with individuals without LBW and with no siblings with LBW, individuals without LBW but with a sibling with LBW had an HR for ESRD of 1.20 (95% CI, 0.91-1.59), individuals with LBW but no siblings with LBW had an HR of 1.59 (95% CI, 1.18-2.14), and individuals with LBW and a sibling with LBW had an HR of 1.78 (95% CI, 1.26-2.53). Similar results were observed for individuals who were small for gestational age (SGA). Separate analyses for the association of age 18 to 42 years and noncongenital ESRD showed stronger associations for SGA than for LBW, and the associations were not statistically significant for age 18 to 42 years for LBW., Limitations: Follow-up only until 42 years of age., Conclusions: LBW and SGA are associated with higher risk for ESRD during the first 40 years of life, and the associations were not explained by familial factors. Our results support the hypothesis that impaired intrauterine nephron development may be a causal risk factor for progressive kidney disease., (Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Background: To compare pregnancy complications and birth outcomes for women experiencing nausea and vomiting in pregnancy, or nausea only, with symptom-free women., Methods: Pregnancies from the Norwegian Mother and Child Cohort Study (n = 51 675), a population-based prospective cohort study, were examined. Data on nausea and/or vomiting during gestation and birth outcomes were collected from three questionnaires answered between gestation weeks 15 and 30, and linked with data from the Medical Birth Registry of Norway. Chi-squared tests, one way analysis of variance, multiple linear and logistic regression analyses were used., Results: Women with nausea and vomiting (NVP) totalled 17 070 (33%), while 20 371 (39%) experienced nausea only (NP), and 14 234 (28%) were symptom-free (SF). When compared to SF women, NVP and NP women had significantly increased odds for pelvic girdle pain (adjusted odds ratio, aOR, 2.26, 95% confidence interval, 95% CI, 2.09-2.43, and aOR 1.90, 95% CI, 1.76-2.05, respectively) and proteinuria (aOR 1.50, 95% CI 1.38-1.63, and 1.20, 95% CI 1.10-1.31, respectively). Women with NVP also had significantly increased odds for high blood pressure (aOR 1.40, 95% CI 1.17-1.67) and preeclampsia (aOR 1.13, 95% CI 1.01-1.27). Conversely, the NVP and NP groups had significantly reduced odds for unfavourable birth outcomes such as low birth weight infants (aOR 0.72, 95% CI 0.60-0.88, and aOR 0.73, 95 % CI 0.60-0.88, respectively) and small for gestational age infants (aOR 0.78, 95% CI 0.73-0.84, and aOR 0.87, 95% CI 0.81-0.93, respectively)., Conclusions: We found that women with NVP and NP are more likely to develop pregnancy complications, yet they display mostly favourable delivery and birth outcomes.

Background: Numerous studies have focused the association between low birthweight and later disease. Our objective was to study the association between birthweight and later adult smoking and thereby explore a possible mechanism for the association between low birthweight and later adult disease., Methods: We studied associations between birthweight of women (n=247704) born in 1967-1995 and smoking habits at the end of their pregnancy 13-42 years later in a prospective, population-based cohort study from The Medical Birth Registry of Norway. Similarly, the association between birthweight of men (n=194393) and smoking habits of their partners were assessed. Finally, we studied the relation between smoking habits of the participating women and the cause specific death of their mothers (n=222808)., Results: Twenty per cent of women with birthweight less than 2000 g were adult daily smokers compared with 11% with birthweight 4000-4499 g [relative risk=1.8, 95% confidence interval 1.4, 2.2]. Similarly, we found an association between men's birthweight and their partners smoking habits. Mothers of smoking women had doubled risk of dying from lung cancer and from cardiovascular disease compared with mothers of non-smoking women., Conclusions: Being born with low birthweight is associated with smoking in adulthood. Associations of adult smoking with partners' birthweight and mothers' smoking-related causes of death suggest a shared smoking environment, and may account for some of the established association between birthweight and later cardiovascular disease., (© 2014 The Authors. Paediatric and Perinatal Epidemiology Published by John Wiley & Sons Ltd.)

Objective: The objective of this study was to explore the association between sexual violence and neonatal outcomes., Design: National cohort study., Setting: Women were recruited to the Norwegian Mother and Child Cohort Study (MoBa) while attending routine ultrasound examinations from 1999 to 2008., Population: A total of 76 870 pregnant women., Methods: Sexual violence and maternal characteristics were self-reported in postal questionnaires during pregnancy. Neonatal outcomes were retrieved from the Medical Birth Registry of Norway (MBRN). Risk estimations were performed with linear and logistic regression analysis., Outcome Measures: gestational age at birth, birth weight, preterm birth (PTB), low birth weight (LBW) and small for gestational age (SGA)., Results: Of 76 870 women, 18.4% reported a history of sexual violence. A total of 4.7% delivered prematurely, 2.7% had children with a birth weight <2500 g and 8.1% children were small for their gestational age. Women reporting moderate or severe sexual violence (rape) had a significantly reduced gestational length (2 days) when the birth was provider-initiated in an analysis adjusted for age, parity, education, smoking, body mass index and mental distress. Those exposed to severe sexual violence had a significantly reduced gestational length of 0.51 days with a spontaneous start of birth. Crude estimates showed that severe sexual violence was associated with PTB, LBW and SGA. When controlling for the aforementioned sociodemographic and behavioural factors, the association was no longer significant., Conclusions: Sexual violence was not associated with adverse neonatal outcomes. Moderate and severe violence had a small but significant effect on gestational age; however, the clinical influence of this finding is most likely limited. Women exposed to sexual violence in this study reported more of the sociodemographic and behavioural factors associated with PTB, LBW and SGA compared with non-abused women., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Background: It is well documented that heightened levels of parenting stress have a negative influence on children's socio-emotional and behavioral development. Parenting stress may therefore be regarded as an outcome variable in its own right. This study investigated whether a sensitizing intervention influences stress reported by parents of prematurely born children until the children were age nine., Methods: Preterm infants (N = 146, birth weight <2,000 g) were randomized to intervention (N = 72) with the Mother-Infant Transaction Program (MITP) or a preterm control group (N = 74) that received standard hospital care. A term reference group comprised 75 healthy, full-term neonates. Parents reported on the Parenting Stress Index (PSI) when the children were 6 months, 1, 2, 3, 5, 7 years old and on the PSI-Short Form (PSI-SF) at age 9. Main outcomes were the mother's and father's reports of total, child and parent-related stress. Cross-sectional and longitudinal analyses were performed using linear mixed models (LMM), taking dependency in the data caused by twin pairs and repeated measures into account. Response rates were high across all follow-ups, and still reached 85% from mothers and 72% from fathers at 9 years., Results: Mothers in the intervention group reported better longitudinal development of child-related stress than mothers of preterm controls, as they perceived their children as being more adaptable and less moody throughout childhood until the age of seven. Less stress in the intervention group was revealed by cross-sectional analysis of maternal reports at all ages, while fathers reported similar differences at ages three and five. Parents in the intervention group reported stronger agreement on several stress scores on several occasions. Fathers with high interventional participation (mean 54%) reported significantly less stress at age nine than those who participated less. Both parents in the intervention group reported levels of stress similar to those experienced by the term reference group at all follow-ups, while differences between the preterm control and term reference groups increased., Conclusions: This early intervention reduces stress among parents of prematurely born children to a level reported by parents of term-born children and enhances agreement between parents., Trial Registration: Clinical Trials Gov identifier NCT00222456, 05.09.2005.

Background: Excessive gestational weight gain (GWG) is associated with pregnancy complications, and Norwegian Health Authorities have adopted the GWG recommendations of the US Institute of Medicine and National Research Council (IOM). The aim of this study was to evaluate if a GWG outside the IOM recommendation in a Norwegian population is associated with increased risk of pregnancy complications like hypertension, low and high birth weight, preeclampsia, emergency caesarean delivery, and maternal post-partum weight retention (PPWR) at 6 and 18 months., Methods: This study was performed in 56 101 pregnant women included in the prospective national Norwegian Mother and Child Cohort Study (MoBa) in the years 1999 to 2008. Women who delivered a singleton live born child during gestational week 37 to 42 were included. Maternal prepregnant and postpartum weight was collected from questionnaires at 17th week of gestation and 6 and 18 months postpartum., Results: A weight gain less than the IOM recommendations (GWG < IOM rec.) increased the risk for giving birth to a low weight baby among normal weight nulliparous women. A weight gain higher than the IOM recommendations (GWG > IOM rec.) significantly increased the risk of pregnancy hypertension, a high birth weight baby, preeclampsia and emergency cesarean delivery in both nulliparous and parous normal weight women. Similar results were found for overweight women except for no increased risk for gestational hypertension in parous women with GWG > IOM rec. Seventy-four percent of the overweight nulliparous women and 66% of the obese women had a GWG > IOM rec. A GWG > IOM rec. resulted in increased risk of PPWR > 2 kg in all weight classes, but most women attained their prepregnant weight class by 18 months post-partum., Conclusions: For prepregnant normal weight and overweight women a GWG > IOM rec. increased the risk for unfavorable birth outcomes in both nulliparous and parous women. A GWG > IOM rec. increased the risk of a PPWR > 2 kg at 18 months in all weight classes. This large study supports the Norwegian Health authorities' recommendations for normal weight and overweight women to comply with the IOM rec.

Background: Cranberry is one of the most commonly used herbs during pregnancy. The herb has been used traditionally against urinary tract infections. No studies are found that specifically address the risk of malformations after use of cranberry during pregnancy. The aim of the study was to investigate the safety of cranberry use during pregnancy, including any effects on congenital malformations and selected pregnancy outcomes., Methods: The study is based on data from The Norwegian Mother and Child Cohort Study including more than 100,000 pregnancies from 1999 to 2008. Information on use of cranberry and socio-demographic factors was retrieved from three self-administered questionnaires completed by the women in pregnancy weeks 17 and 30, and 6 months after birth. Information on pregnancy outcomes was retrieved from the Medical Birth Registry of Norway., Results: Among the 68,522 women in the study, 919 (1.3%) women had used cranberry while pregnant. We did not detect any increased risk of congenital malformations after use of cranberry. Furthermore, the use of cranberry was also not associated with increased risk for stillbirth/neonatal death, low birth weight, small for gestational age, preterm birth, low Apgar score (<7), neonatal infections or maternal vaginal bleeding in early pregnancy. Although an association was found between use of cranberry in late pregnancy and vaginal bleeding after pregnancy week 17, further sub-analyses of more severe bleeding outcomes did not support a significant risk., Conclusions: The findings of this study, revealing no increased risk of malformations nor any of the following pregnancy outcomes; stillbirth/neonatal death, preterm delivery, low birth weight, small for gestational age, low Apgar score and neonatal infections are reassuring. However, maternal vaginal bleeding should be investigated further before any firm conclusion can be drawn. Treatment guidelines on asymptomatic bacteriuria in pregnancy recommend antimicrobial therapy as the first line treatment. According to our data and the outcomes studied, cranberry does not appear to be a harmful adjunctive self-treatment.

Background: Hyperemesis gravidarum (HG) characterized by excessive nausea and vomiting in early pregnancy, is reported to be associated with increased risks for low birthweight (LBW), preterm birth (PTB), small-for-gestational-age (SGA) and perinatal death. Conflicting results in previous studies underline the necessity to study HG's potential effect on pregnancy outcomes using large cohorts with valid data on exposure and outcome measures, as well as potential confounders. This study aims to investigate associations between HG and adverse pregnancy outcomes using the Norwegian Mother and Child Cohort Study (MoBa)., Methods: All singleton pregnancies in MoBa from 1998 to 2008 were included. Multivariable regression was used to estimate relative risks, approximated by odds ratios, for PTB, LBW, SGA and perinatal death. Linear regression was applied to assess differences in birthweight and gestational age for children born to women with and without HG. Potential confounders were adjusted for., Results: Altogether, 814 out of 71,468 women (or 1.1%) had HG. In MoBa HG was not associated with PTB, LBW or SGA. Babies born to women with HG were born on average 1 day earlier than those born to women without HG; (-0.97 day (95% confidence intervals (CI): -1.80 - -0.15). There was no difference in birthweight when maternal weight gain was adjusted for; (23.42 grams (95% CI: -56.71 - 9.86). Babies born by women with HG had lower risk for having Apgar score < 7 after 1 minute (crude odds ratio was 0.64 (95% CI: 0.43 - 0.95)). No differences between the groups for Apgar score < 7 after 5 minutes were observed. Time-point for hospitalisation slightly increased differences in gestational age according to maternal HG status., Conclusions: HG was not associated with adverse pregnancy outcomes. Pregnancies complicated with HG had a slightly shorter gestational length. There was no difference in birth weight according to maternal HG-status. HG was associated with an almost 40% reduced risk for having Apgar score < 7 after 1 minute, but not after 5 minutes. The clinical importance of these statistically significant findings is, however, rather limited.

Knowledge on triptan safety during pregnancy remains limited to their class effect or studies on sumatriptan. Our aim was to evaluate the individual effect of four most frequently used triptans on several pregnancy outcomes. We used the Norwegian prescription database to access information on triptans redeemed by pregnant women living in Norway between 2004 and 2007. This database was linked to the Medical Birth Registry of Norway covering every institutional delivery in Norway and providing information on pregnancy, delivery, maternal and neonatal health. Estimates of associations with pregnancy outcomes were obtained by Generalised Estimation Equations analysis. Of the 181,125 women in our study, 1,465 (0.8%) redeemed triptans during pregnancy, and 1,095 (0.6%) redeemed triptans before pregnancy only (disease comparison group). The population comparison group comprised the remaining 178,565 women. Using this group as reference, we found no associations between triptan redemption during pregnancy and congenital malformations. Second trimester redemption was associated with postpartum haemorrhage (adjusted OR 1.57; 95% CI 1.19-2.07). The disease comparison group had an increased risk of major congenital malformations (adjusted OR 1.48; 95% CI 1.11-1.97), low birth weight (adjusted OR 1.39; 95% CI 1.08-1.81), and preterm birth (adjusted OR 1.30; 95% CI 1.06-1.60). The association of triptans with postpartum hemorrhage could be attributable to decreased platelet agreeability occurring in severe migraine. Likewise, the increased risk of major congenital malformations and other adverse pregnancy outcomes in the disease comparison group might be attributable to migraine severity.

Objective: To investigate the individual effects of ibuprofen, diclofenac, naproxen, and piroxicam on pregnancy outcome., Design: Cohort study., Setting: Norwegian population., Population: A total of 90 417 women and singleton child pairs., Methods: The Norwegian Mother and Child Cohort Study and Medical Birth Registry of Norway data sets were used., Main Outcome Measures: Infant survival, congenital malformations, structural heart defects, neonatal complications, haemorrhage during pregnancy and postpartum, asthma at age of 18 months., Results: One or more of the four nonsteroidal anti-inflammatory drugs (NSAIDs) were used by 6511 pregnant women (7.2%). No effect on rates of infant survival, congenital malformation, or structural heart defects was found. The use of ibuprofen in the second trimester was significantly associated with low birthweight (adjusted OR 1.7, 95% CI 1.3-2.3), and ibuprofen use in the second and third trimesters was significantly associated with asthma in 18-month-old children (adjusted OR 1.5, 95% CI 1.2-1.9; adjusted OR 1.5, 95% CI 1.1-2.1). The use of diclofenac in the second trimester was significantly associated with low birthweight (adjusted OR 3.1, 95% CI 1.1-9.0), whereas diclofenac use in the third trimester was significantly associated with maternal vaginal bleeding (adjusted OR 1.8, 95% CI 1.1-3.0). No associations with other neonatal complications were found., Conclusions: The lack of associations with congenital malformations is reassuring. The significant association between diclofenac and ibuprofen use late in pregnancy, and maternal bleeding and asthma in the child, respectively, is consistent with their pharmacological effects. The increased risk of low birthweight may partly have been caused by underlying inflammatory conditions, and was reassuringly similar to the expected baseline risk of low birthweight., (© 2013 The Authors BJOG An International Journal of Obstetrics and Gynaecology © 2013 RCOG.)

Aims: We aimed to explore associations between drugs dispensed to the father prior to conception and pregnancy outcomes, such as pre-term birth, perinatal mortality, foetal growth retardation and birth defects., Methods: In this cohort study, two population-based registries, the Medical Birth Registry of Norway and the Norwegian Prescription Database, were linked. The study cohort consisted of 340 000 pregnancies in 2004-10. The association between specific drugs dispensed to the fathers during the last 3 months prior to conception and pregnancy outcomes was explored by estimating odds ratios (ORs) using multivariate logistic regression., Results: About one quarter (26%) of the fathers were dispensed at least one drug during the last 3 months prior to conception and 1.3% were dispensed at least one drug requiring special attention. Overall, the odds of different adverse pregnancy outcomes were not increased when the father had been dispensed drugs, i.e. the OR and 95% confidence intervals (CIs) for any birth defect when the fathers had been dispensed any drug were 0.99 (0.94, 1.0). When the fathers had been dispensed diazepam we found increased risk of perinatal mortality and growth retardation, with OR and 95% CIs of 2.2 (1.2, 3.9) and 1.4 (1.2, 1.6), respectively., Conclusions: Large studies are necessary to reveal increased risk of rare outcomes as specific birth defects. Our study did not indicate that paternal drug exposure is an important risk factor for adverse pregnancy outcomes., (© 2012 The Authors. British Journal of Clinical Pharmacology © 2012 The British Pharmacological Society.)

Low birth weight is associated with increased risk of cardiovascular disease and type 2 diabetes in later life. The fetal insulin hypothesis suggests that shared genetic factors partly explain this association. If fetal genes predispose to both low birth weight and cardiovascular disease in adulthood, fathers of offspring with low birth weight should display an unfavorable profile of cardiovascular risk factors. To study this, the authors linked data on more than 14,000 parents, collected from the second Health Study of Nord Trøndelag County, Norway (HUNT 2, 1995-1997), to offspring data from the Norwegian Medical Birth Registry (1967-2005). Linear regression was used to study associations of offspring birth weight for gestational age with the parents' body mass index, waist circumference, blood pressure, glucose, and serum lipids. All analyses were adjusted for shared environment by means of the socioeconomic measures, lifestyle, and cardiovascular risk factors of the partner. The authors found that low offspring birth weight for gestational age was associated with increased paternal blood pressure, body mass index, waist circumference, and unfavorable levels of glucose and lipids. For mothers, associations similar to those for fathers were found for blood pressure, whereas associations in the opposite direction were found for glucose, lipids, and body mass index. The paternal findings strengthen the genetic hypothesis.

Background: Women with familial hypercholesterolemia (FH) are prone to early cardiovascular disease and death. It is unknown whether FH adversely affects pregnant women and birth outcomes. We determined whether heterozygous FH women are at higher risk of premature birth (<37 gestational weeks), delivering children with low birth weight (<2500 g) and/or with congenital malformations compared to women in general., Methods and Results: We linked information from the Medical Genetics Laboratory with that of the Medical Birth Registry of Norway. We included 1869 FH women (≥ 14 years) from the Medical Genetics Laboratory and about 2 million (general population) from the Medical Birth Registry of Norway during the period 1967 to 2006. The registry match resulted in analysis of 2319 births of 1093 women with heterozygous FH. The mean (SD) prepregnancy total cholesterol concentration was 9.59 (2.06) mmol/L (370 [80 mg/dL]), whereas the concentration of total cholesterol was not available during pregnancy. The frequencies of prematurity, low birth weight, and congenital malformations for the 40-year period in the FH population were 6.8, 5.0, and 3.3, respectively. The corresponding values for the general population were 6.2, 5.2, and 3.2. The corresponding odds ratios were 1.11 (95 confidence interval 0.94-1.31; P=0.23), 0.96 (0.79-1.15; P=0.64), and 1.09 (0.87-1.37; P=0.45)., Conclusions: Women with FH do not appear to have a higher risk of preterm delivery or of having infants with low birth weight or congenital malformations than women in general, but, although this is unlikely, some undetected bias may obscure the real differences.

Objectives: To assess the association between maternal parvovirus B19 infection and fetal death, birthweight and length of gestation., Design: Case-control study., Setting: Population based., Population: Cases were all 281 women with fetal death within a cohort of 35 940 pregnant woxmen in Norway. The control group consisted of a random sample of 957 women with a live born child., Method: Information on pregnancy outcome was obtained from the Medical Birth Registry of Norway. First trimester serum samples were tested for antibodies against parvovirus B19 (IgM and IgG). In seronegative women, further serum was analysed to detect seroconversion during pregnancy., Main Outcome Measures: Fetal death, length of gestation and birthweight., Results: Two of 281 (0.7%) of the women who experienced fetal death and nine of 957 (0.9%) of the controls had presence of IgM antibodies, crude odds ratio 0.8; 95% CI (0.2-3.5). In initially, seronegative women, 3.1% (2/65) with fetal death and 2.6% (8/307) with a live birth seroconverted, crude odds ratio 1.2; 95% CI (0.2-5.7). Presence of maternal parvovirus-specific IgG or IgM antibodies in the first trimester, or seroconversion during pregnancy were not associated with lower birthweight or reduced length of gestation in live born children, but was associated with low birthweight in stillborn offspring., Conclusion: Maternal parvovirus B19 infection was not associated with fetal death in our study. Very few cases of fetal death may be attributed to maternal parvovirus B19 infection.

Background: It is unknown whether preeclampsia is a risk marker for subsequent end-stage renal disease (ESRD)., Methods: We linked data from the Medical Birth Registry of Norway, which contains data on all births in Norway since 1967, with data from the Norwegian Renal Registry, which contains data on all patients receiving a diagnosis of end-stage renal disease (ESRD) since 1980, to assess the association between preeclampsia in one or more pregnancies and the subsequent development of ESRD. The study population consisted of women who had had a first singleton birth between 1967 and 1991; we included data from up to three pregnancies., Results: ESRD developed in 477 of 570,433 women a mean (+/-SD) of 17+/-9 years after the first pregnancy (overall rate, 3.7 per 100,000 women per year). Among women who had been pregnant one or more times, preeclampsia during the first pregnancy was associated with a relative risk of ESRD of 4.7 (95% confidence interval [CI], 3.6 to 6.1). Among women who had been pregnant two or more times, preeclampsia during the first pregnancy was associated with a relative risk of ESRD of 3.2 (95% CI, 2.2 to 4.9), preeclampsia during the second pregnancy with a relative risk of 6.7 (95% CI, 4.3 to 10.6), and preeclampsia during both pregnancies with a relative risk of 6.4 (95% CI, 3.0 to 13.5). Among women who had been pregnant three or more times, preeclampsia during one pregnancy was associated with a relative risk of ESRD of 6.3 (95% CI, 4.1 to 9.9), and preeclampsia during two or three pregnancies was associated with a relative risk of 15.5 (95% CI, 7.8 to 30.8). Having a low-birth-weight or preterm infant increased the relative risk of ESRD. The results were similar after adjustment for possible confounders and after exclusion of women who had kidney disease, rheumatic disease, essential hypertension, or diabetes mellitus before pregnancy., Conclusions: Although the absolute risk of ESRD in women who have had preeclampsia is low, preeclampsia is a marker for an increased risk of subsequent ESRD., (2008 Massachusetts Medical Society)

To investigate the influence of maternal multiple sclerosis (MS) on pregnancy, we compared pregnancy, delivery and birth outcome in births prior to onset of MS (pre MS), between MS onset and diagnosis (early MS), and after diagnosis of MS (manifest MS). Mothers with MS were identified through linkage of the Norwegian MS Registry and the Medical Birth Registry of Norway (1967-2002). All pre MS births (n = 1910), early MS births (n = 555), and manifest MS births (n = 308) were compared. There was a significantly lower mean birth weight in term births (adjusted for gestation in weeks, mother's age, time period and caesarean section) in the manifest MS compared to the pre MS group (P = 0.046). The rate of birth complications and interventions did not differ between the three groups. Manifest MS in birth-giving mothers seems to affect birth weight.

Case-control studies have shown an association between low birth weight and risk for renal failure. The Medical Birth Registry of Norway, which comprises data on all births in Norway since 1967, and the Norwegian Renal Registry, which comprises data on all patients who have developed ESRD in Norway since 1980, were used to examine whether birth-related variables were associated with risk for ESRD. Of the 2,183,317 children born between 1967 and 2004, 526 were found in the ESRD registry. Compared with birth weight in the 10th to 90th percentiles, births <10th percentile had a relative risk (RR) for ESRD of 1.7 (95% confidence interval 1.4 to 2.2; P < 0.001). Births with a weight for gestational age <10th percentile had an RR of 1.5 (95% confidence interval 1.2 to 1.9; P = 0.002). These associations were virtually identical after adjustment for birth-related confounders such as congenital malformations, multiple delivery, maternal age at birth, and maternal preeclampsia. Low birth weight was more strongly associated with development of ESRD during the first 14 years of life than after age 15. Low birth weight and low birth weight for gestational age were similarly associated with multiple causes of ESRD. In conclusion, in this cohort study with a maximum follow-up of 38 years, low birth weight and intrauterine growth restriction were associated with increased risk for ESRD.

Birth weight is associated with later-life cardiovascular risk. A new study by Romundstad et al. (Am J Epidemiol 2007;166:1359-1364) challenges us to consider influences on birth weight with respect to timing and type. Timing of effects on birth weight, according to the "fetal origins hypothesis," is in utero. Alternatively, familial aggregation--genetics or shared environment--may explain birth weight and suggests prepregnancy influences. The Romundstad et al. findings support familial effects: maternal metabolic factors predicted birth weight for gestational age. However, because maternal physiology sets the fetal environment, these data do not necessarily counter the fetal origins hypothesis. Types of maternal metabolic influences demonstrated by Romundstad et al. include elevations in blood pressure being associated with lower birth weight for gestational age, whereas unfavorable glucose and lipid levels were associated with higher birth weight. These findings are consistent with the authors prior hypothesis that vascular dysfunction and metabolic profile (glucose and lipids) have divergent effects during pregnancy. Moreover, these new data underscore that both extremes of birth weight may be related to cardiovascular risk. Few data sets contain prepregnancy, pregnancy, and childhood information. Without all such time points, life course effects will remain only partially understood. It is hoped that studies such as the forthcoming National Children's Study will generate critical understanding of this issue.

Low birth weight of offspring has been associated with increased risk of maternal cardiovascular mortality, and cardiovascular risk factors measured within pregnancy have been related to offspring birth weight. It is not clear whether cardiovascular risk factors assessed prior to pregnancy are associated with the offspring's birth weight. The authors combined baseline data from 3,461 women in the HUNT Study (1995-1997) and data on deliveries from the Medical Birth Registry of Norway up to 2005. They used linear regression to prospectively study associations between diastolic and systolic blood pressures, concentrations of triglycerides, serum total cholesterol, and high density lipoprotein cholesterol measured before conception and birth weight for gestational age of the offspring. Blood pressure measured before pregnancy was inversely associated with birth weight for gestational age, whereas unfavorable levels of serum total cholesterol, high density lipoprotein cholesterol, triglycerides, and glucose were positively associated with birth weight for gestational age. Thus, women with relatively high blood pressure tend to deliver small babies, whereas women with unfavorable lipid levels tend to give birth to large babies, suggesting reduced glucose tolerance. These findings suggest that low as well as high birth weight of the offspring may indicate increased cardiovascular risk for the mother.

The aim of this study was to estimate the impact of birthweight on the risk of sensorineural hearing loss in children. The study was a nested case-control study. Cases (n = 327) were identified through the Norwegian county registers of children with hearing loss, and controls (n = 391 992) were all children without hearing loss born in the same counties, identified through the Norwegian Medical Birth Registry of Norway. Case definition was mean sensorineural hearing loss (MHL) > or =35 decibel (dB) hearing level (HL) in the better-hearing ear averaged over the pure-tone hearing thresholds at 500, 1000 and 2000 Hz, diagnosed before the age of 5 years. Birthweight <1500 g, as compared with 3500-3999 g, gave an adjusted odds ratio for sensorineural hearing loss of 6.3 [95% CI 2.4, 16.4], controlled for gestational age, gender, parity, maternal age and concurrent birth defects. The risk of hearing loss decreased with increasing birthweights, with adjusted odds ratios of 4.4, 3.8, 1.7 and 1.4 for the birthweights 1500-1999, 2000-2499, 2500-2999 and 3000-3499 g respectively. The risk of both mild to moderate (MHL 35-70 dBHL) and severe/profound hearing losses (MHL >70 dBHL) were influenced by birthweight.

Population-based twin data were used to test (a) whether lower birthweight confers a greater risk of adult health disorders, and (b) whether within-pair birthweight differences in twins explain discordance for health outcomes. The sample consisted of 1201 monozygotic (MZ) male twins, 1048 dizygotic (DZ) male twins, 1679 MZ female twins, 1489 DZ female twins, and 2423 opposite-sex DZ twins, born in Norway between 1967 and 1979. The relationship between birthweight and self-reported health outcomes were studied using multivariable logistic regression. In the full sample (n = 7840), birthweight was negatively associated with risk for nearsightedness (odds ratio OR = 0.76, 95% CI: 0.65 - 0.92) and minimal brain disorder (OR = 0.27, 95% CI: 0.16-0.44) when adjusted for gestational age, sex, zygosity, age, education and body mass index after correction for intraclass correlations and multiple comparisons. Within-pair analysis of 159 MZ and 224 DZ pairs revealed that myopic twins were on average 2 g (p = .966) and 64 g (p = .040) lighter than nonmyopic twins in MZ and DZ pairs respectively, suggesting that genetic factors may play an important role in the associations between birthweight and nearsightedness. Within-pair analysis of twins discordant for a minimal brain disorder indicated that affected twins were 80 g (p = .655) and 85 g (p = .655) lighter than their healthy co-twins in MZ and DZ pairs respectively, although there were only 2 MZ and 2 DZ discordant pairs.

Background: In a number of studies, birthweight has been associated with cognition and educational attainment into adult age. However, the association is not clear between birthweight and work participation in adulthood. We investigated this association assessing to which extent it was influenced by circumstances concerning family background or disease in early life., Methods: Through linkage between several national registers containing personal information from birth into adult age we established a longitudinal, population-based cohort study. Study participants were all 308 829 singletons born in Norway in 1967-1971 as registered by the Medical Birth Registry of Norway who were national residents at age 29. The study outcome was unemployment defined as a lack of personal income among people who were not under education in the calendar year of their 29th birthday as registered by the National Insurance Administration and Statistics Norway., Results: Birthweight below the standardized mean was associated with unemployment. The risk of unemployment increased by decreasing birthweight for both women and men and also after adjustment for potential confounding factors. The association was evident both in people with or without social disadvantage, as well as people with or without childhood disease. Still, birthweight below the standardized mean explained much less of the unemployment risk than did social disadvantage (attributable fractions 8.0% versus 28.3% for women and 10.0% versus 40.2% for men)., Conclusion: Birthweight below the standardized mean was independently associated with unemployment at age 29, also in the normal birthweight range.

Objective: To compare the effects on pregnancy outcomes of changing partner between the first two births with having the same partner for both births., Design: Prospective population study., Setting: Norway., Participants: 31 683 women who changed partner between their first two births and 456 458 women with the same partner for both births., Results: After adjustment for maternal age and education, interval between births, and decade of birth, the risk of adverse pregnancy outcomes for the second birth was higher for women who changed partner between the first two births compared with those who had the same partner for both births: preterm birth (< 37 weeks; relative risk 2.0, 95% confidence interval 1.9 to 2.1), low birth weight (< 2500 g; 2.5, 2.3 to 2.6), and infant mortality (1.8, 1.6 to 2.1). For the first birth, the risk of these adverse pregnancy outcomes was only slightly higher for mothers who subsequently had a second birth with another partner., Conclusion: Women who change partner between their first two births are at an increased risk of delivering a preterm, low birthweight baby with an increased risk of infant mortality compared with women who have the same partner for both births.

Objectives: This study assessed the occurrence of perinatal death, low birthweight, preterm birth, and birth defects (total, major, neural tube defects, total cleft, cleft palate, hypospadias, and Down syndrome) in the offspring of airline pilots and cabin attendants., Methods: A cohort of offspring of airline pilots and cabin attendants was established and characterized in terms of parental exposure to cosmic radiation the year before birth or ever. Pregnancy outcome was derived from the Medical Birth Register of Norway. The reference group comprised offspring of parents without occupational exposure to cosmic radiation., Results: No deviant risks were observed for the offspring of male pilots, either for the year preceding birth (N=2,111) or ever (N=2,356). Specific birth outcomes were fewer for the pilots than for the referents (N=1,621,186), except for Down syndrome, which was more frequent [odds ratio (OR) 1.41, 95% confidence interval (95% CI) 0.53-3.76]. For exposure the year preceding birth (N=2,512), the risk of low birthweight was lower for the female cabin attendants than for the referents (adjusted OR 0.83, 95% CI 0.69-1.00), while Down syndrome was more frequent (OR 1.44, 95% CI 0.60-3.47). For exposure ever (N=3346), the risk of low birthweight was lower (OR 0.82, 95% CI 0.70-0.96) for the cabin attendants, while hypospadias (OR 1.18, 95% CI 0.61-3.04) and Down syndrome (OR 1.79, 95% CI 0.03-3.45) were more frequent, Conclusions: In general, offspring of air pilots and cabin attendants do not seem to be at increased risk of adverse pregnancy outcome.

Objective: To study recurrence risks of adverse pregnancy outcome in the second pregnancy in women with rheumatic disease., Methods: In a national population-based cohort study, women with rheumatic disease recorded from 1967 to 1995 in the Medical Birth Registry of Norway were compared with mothers without such diagnoses with regard to recurrence risks of adverse pregnancy outcomes in the second pregnancy. The odds ratios (ORs) of all outcomes were adjusted for maternal age, those of cesarean delivery for time period, and those of preeclampsia for interpregnancy interval., Results: Women with rheumatic disease an dadverse pregnancy outcome in the first pregnancy had a statistically significant higher recurrence risk of the same event in the second pregnancy than women without rheumatic disease (preeclampsia: OR 2.22; 95% confidence interval [CI] 1.18, 4.19) (cesarean delivery: OR 1.52; 95% CI 1.05, 2.21) (preterm birth: OR 1.86; 95% CI 1.12, 3.11). In women with rheumatic disease diagnosed between the first and second births, a significantly increased recurrence risk of low birth weight occurred. Women with rheumatic disease also had a higher occurrence of markers for placental dysfunction (preeclampsia, preterm birth, or small for gestational age) in the second birth after any of these outcomes in the first birth (OR 1.35; 95% CI 1.02, 1.78) (35.1% versus 29.2%)., Conclusion: The recurrence risk of an adverse outcome in the second pregnancy is increased in any woman, but was even higher in women with a rheumatic disease. These patients should be counseled accordingly, be closely monitored during pregnancy, and have access to appropriate subspecialists.

Infants with congenital malformations have on average lower birth weight than do infants without malformations. Preterm delivery and low birth weight are known to recur in sibships. The aim of the study was to compare the birth weight of siblings to malformed infants with the birth weight of infants in families without malformed infants. Data were from the Medical Birth Registry in Norway from 1967 to 1998. Births were linked to their mothers through the unique personal identification number, providing sibship files with the mother as the observation unit. The study was based on 551,478 mothers with at least two singleton infants and 209,423 mothers with at least three singletons. The authors grouped the families according to whether and in which birth order an infant had a registered congenital malformation and compared birth weight and gestational age between infants of the same birth order in families with malformations and without. Overall, in families where one or two infants had a congenital malformation, the crude and adjusted mean birth weight of nonmalformed siblings did not differ from that of infants in unaffected families, whereas it was significantly reduced for the malformed infant itself. We conclude that reduced birth weight associated with congenital anomalies is specific to the affected pregnancy.

Background: An investigation of the prevalence of cerebral palsy in relation to neonatal intensive care., Material and Methods: Population based study in live-born children with birthweight > or = 500 g in the Norwegian county of Vestfold over the 25-year period 1970-94 (n = 58,448). Retrospective and prospective control of cases (cases with a postneonatal origin of cerebral palsy excluded) with a minimum follow-up to four years of age., Results: Cerebral palsy was diagnosed in 139 cases (2.4 per 1,000). The prevalence declined from 2.8 per 1,000 in the first five-year cohort born 1970-74, to 2.2 per 1,000 in children born in each of the three five-year cohorts born 1980-84, 1985-89, and 1990-94 (p = 0.24). The neonatal mortality rate declined significantly from 8.7 per 1,000 in the first to 2.8 per 1,000 in the last five-year cohort (p < 0.0001). The low birthweight (500-2,499 g) rate in live-born infants increased significantly in 1990-94 compared to 1985-89 (4.5% vs 3.9% respectively; p < 0.05). After a local ventilator treatment programme (operative from 1989) was established, transports of infants with severe respiratory distress syndrome to the regional hospital declined from 3 per 1,000 live-born infants to 1 per 1,000 (p < 0.0001)., Interpretation: A decentralised neonatal intensive care programme can be developed, with substantial decline in neonatal mortality without a corresponding increase in cerebral palsy prevalence.

Background: Sociodemographic studies of hyperemesis gravidarum are conflicting. During the last few years, there has been a clinical impression in Norway that immigrants are more afflicted than ethnic Norwegians., Methods: Of 175 patients hospitalized with the diagnosis hyperemesis gravidarum 1993-1997, 120 had complete records and were compared to a control group of 115 patients without hyperemesis gravidarum, drawn at random from the labor ward protocol., Variables: Ethnicity, age, height, weight at the beginning and at the end of pregnancy, body mass index, gravidity, parity, smoking, gestational age at labor, birth weight, placental weight. The patient's first name was used as an indication of ethnicity. Having a non-Norwegian name means, in the majority of cases, being a first generation immigrant from a developing country., Statistics: SPSS statistical package for regression analyses, the chi-square test with Yates correction and the Mann-Whitney U-test., Results: Risk factors for hyperemesis: non-Norwegian name (OR 3.4, 95% CI 1.5-7.6), female sex of the infant (OR 2.6, 95% CI 1.3-5.3), gravidity number (OR 1.4, 95% CI 1.1-1.9). These two last variables were of significance only in patients with a Norwegian name. The hyperemesis group had a lower weight gain and birth weight. In a stepwise multiple regression birth weight (g) was dependent on weight increase (kg) (B=19.0, p=0.001), weight in early pregnancy (kg) (B=8.0, p =0.02) and parity (B= 107.1, p=0.02). Hyperemesis, when corrected for weight increase, did not influence birth weight., Conclusions: Risk factors vary between different populations. Hyperemesis patients are at risk of having infants with reduced growth.

Women's experiences of different kinds of abusive behavior by their partners were studied in relation to birth weight of the women's infants and other pregnancy outcome measures. Eighty-four women who delivered a low-birth-weight (< 2500 g) infant (cases) and 90 women who delivered an infant with higher birth weight (controls) were interviewed in a case-control study. Information about the partners' behavior during conflicts were obtained by use of a modified Conflict Tactics Scale. Different interpersonal conflict behaviors were categorized as negative verbal interaction or moderate or severe physical abuse. Women who had experienced moderate or severe violence in a relationship also had experienced negative verbal interaction from their partner. Low birth weight was not associated with experiences of any interpersonal conflict behavior in the total sample (OR 0.75, 95% CI 0.42-1.37). Among women with a low birth weight infant, mean birth weight was 261 g lower among those who reported any interpersonal conflict behavior during pregnancy. Birth of a low-birth-weight infant was not associated with abuse in a wide sense. Also, such abuse was unassociated with a variety of other complications during pregnancy, lifestyle characteristics, or pregnancy outcome measures.

To describe trends in low birth weight (less than 2,500 g), the authors analyzed 1.7 million live births and stillbirths registered between 1967 and 1995 in the Medical Birth Registry of Norway. The proportion of low birth weight infants declined from 5.3% in 1967 to 4.5% in 1979 and was followed by a steady increase that reached 5.3% in 1995. Similar trends were observed in the proportion of preterm births. Mean birth weight increased from 3,456 g in 1967 to 3,518 g in 1995. From 1979 to 1987, the increase in the prevalence of low birth weight was related to single births, and after 1987 it was related to multiple births, which increased from 2.3% of all births in 1987 to 3.1% in 1995. The proportion of low birth weight in births occurring after 37 weeks of gestation declined continuously, resulting in low birth weight births' to an increasing extent being made up of births occurring before 37 weeks of gestation. In an ecologic analysis based on county of maternal residence, the increase in low birth weight among single births was accounted for by an increase in deliveries with induction of labor or cesarean section. The authors conclude that the overall proportion of low birth weight births is not a good indicator of health in a population with extensive use of obstetric procedures that affect gestational age or assisted fertilization, which increases the number of multiple births.

The two objectives of this study were to compare urinary nickel excretion in pregnant women and their newborns living in the Murmansk and Arkhangelsk Counties of Russia with that in comparable Norwegian populations living in Finnmark and the city of Bergen and to assess the influence on pregnancy outcome of different risk variables, specifically urinary nickel concentrations and questionnaire-based anamnestic information. Life-style information and urine samples were collected from 50 consecutive mother-infant pairs from hospital delivery departments in three Russian and three Norwegian communities. Pregnancy outcomes were verified from medical records. Urinary nickel excretion was significantly higher in the Russian communities, independent of the presence of a nickel refinery as a local environmental source. The birth weight and mean body mass index of the newborn children (BMIC) were significantly lower (p < 0.001) in the Russian groups, with or without adjustment for gestational age. A multivariate linear regression analysis indicated that maternal urinary nickel concentration had no impact on birth weight. The maternal body mass index (BMI) and maternal height were positive explanatory variables; maternal urinary creatinine is suggested as a weak negative factor. Smoking was shown to be a strong negative predictor only in the Norwegian group among whom there was a significantly higher smoking frequency (p = 0.005). The significant contribution of a country factor in the predictive model is interpreted to indicate that a number of important risk factors for low birth weight were not identified.

Objectives: This study explored the possible effects of power to control one's own work pace on pregnancy health., Methods: Questionnaires were sent to all parturients in Norway between 16 October and 26 November 1989 for completion prior to discharge from the hospital; 87.2% responded. The study population comprised 3321 respondents with singleton pregnancies and paid work beyond the 3rd month of pregnancy. Power to control work pace was measured as self-reported influence on breaks and work pace and absence of external pacing. Pregnancy health was defined by the prevalence of preeclampsia, disabling posterior pelvic pain, low-back pain, and birthweight of <2500 g for the offspring., Results: Pregnancy health improved with increasing power to control work pace, both in manual and nonmanual work. The risk decreased with increasing control for all 4 outcomes, but the impact on birthweight was restricted to nullipara. After adjustment for age, parity, education, smoking, and manual work, the decreasing trend remained significant for preeclampsia and low birthweight of the first born. In a comparison with women with the highest level of control, the adjusted odds ratios for women with no control were 1.6 [95% confidence interval (95% CI) 0.9-3.1] for preeclampsia, 1.6 (95% CI 1.0-2.4) for disabling posterior pelvic pain, 1.3 (95% CI 1.0-1.8) for low-back pain, and 2.5 (95% CI 0.9-6.8) for low birthweight (nullipara)., Conclusions: Women with power to control their own work pace had better pregnancy health than women without such power. The results suggest increased individual control over work pace as a prime target for job adjustment during pregnancy.

Unlabelled: The aim was to evaluate neuropsychological performance and its pre-, and perinatal predictors in low birth weight (LBW) preschool children. A population-based sample of 137 5-year-old children with birth weights less than 2000 g and without major handicaps was compared with a random sample of 152 normal birth weight term controls. Main assessment tools were all subscales from the Wechsler Preschool and Primary Scale of Intelligence Revised, subscales from the Illinois Test of Psycholinguistic Abilities and tests of manual dexterity and figure copying. The LBW children showed significantly lower mean scores compared to controls on tests of visuo-spatial and visuo-motor abilities, but were comparable to controls in other areas, confounding parental factors were controlled for. 14 of the LBW children, there were signs of maternal chorio-amnionitis. Twelve of these had premature rupture of membranes lasting more than 24 h. These 14 children had a mean performance IQ of 87 (SD 5) compared to 100 (SD 15) for the LBW children without maternal signs of chorio-amnionitis (P = 0.001). Having a small head circumference at birth was a less powerful, but statistically significant predictor of impaired performance., Conclusion: Low birth weight is associated with impaired performance on visuo-spatial and visuo-motor tasks. Signs of maternal chorio-amnionitis and a small head circumference at birth may be risk factors for such impairment.

Blood culture results obtained in a single tertiary neonatal intensive care unit are reviewed. In 4416 admissions occurring over 6 y we identified 206 positive cultures (4.7/100 admissions) growing 234 bacterial and fungal isolates in 182 infants. Very early and early onset positive cultures comprised 17% and 22% each. Gram-positive bacteria dominated in very early (61%), early (91%) and late onset (78%) cultures with coagulase-negative staphylococci (CONS) as the most frequent isolate in all groups (22%, 46% and 55%, respectively). The 3 most frequent isolates following CONS were in very early onset cultures Escherichia coli (19%), anaerobic bacteria (17%) and group B streptococci (GBS) (14%), in early onset cultures Staphylococcus aureus (28%), Enterococci (7%), E. coli (6%) and Viridans streptococci (6%) and in late onset cultures S. aureus (15%), Candida species (8%) and E. coli (5%). Infants < or = 999 g birthweight, representing 6% of the admissions, contracted 37% of the positive blood cultures and nearly half (44%) of the CONS isolates. In these patients, a significant increase (p < 0.001) in the number of positive cultures/100 admissions and in the proportion of positive cultures in conjunction with an intravascular catheter were seen (p < 0.001). An intravascular catheter was more often present when CONS were isolated as compared to other organisms (p < 0.05). 23 positive cultures (11.2%), most frequently E. coli, were associated with a fatal outcome. Our microbiological pattern is dominated by a gram-positive flora, which is in agreement with recent European and North American reports, but differs from earlier Scandinavian studies in the proportion of CONS and GBS reported.

Stillbirth and the mortality rate in low birthweight infants (less than 2,500 g) have been greatly reduced since 1967. 95% of all infants born in 1991-93 whose birthweight was between 500 and 999 g, and who survived to one year of age, would have died under the same circumstances in 1967-69. This improved survival is not, to any appreciable extent, related to an increase in demand at seven years of age for a basic grant or attendance benefit because of cerebral palsy or mental retardation. The number of basic grant and attendance benefits because of eye diseases has been reduced by about half for 7-year olds whose birthweight was low. On the whole, however, the number of basic grant and attendance benefits increased from about 1% in 1974-85 to 2.2% in 1986-94. This increase can be particularly attributed to skin and lung diseases. These results have been obtained by coordinating the record of the Medical Birth Registry of Norway and the records of the Social Security offices for all births (1,566,763) registered during the years 1967-93.

We have investigated the incidence of retinopathy of prematurity (ROP) among premature infants with birth weight less than 1500 g in two Norwegian counties during the years 1989-1993. Two hundred and seven out of 244 such infants (84.8%) were examined at the neonatal intensive care unit; 66 of those examined (31.9%) had a birth weight below 1000 g. ROP was found in 21 patients (10.1%), and stage 3 disease was present in 7 (3.4%). No patient had more advanced ROP than stage 3. Assuming that no cases of stage 3 ROP were missed among the total of 244 children, the incidence of stage 3 disease was 2.9%. The frequency of ROP in this study is compared to that of other population-based studies in the Nordic countries, and incidence differences are discussed.

Background: Little is published about obstetrical problems after treatment of cervical intraepithelial neoplasia with the C02-laser. The aim of this study was to determine the risk of low birth weight in the subsequent pregnancy after laser conization or vaporization in a follow-up study of women treated for cervical intraepithelial neoplasia (CIN). Methods. Of 319 women treated for CIN with the C02-laser in the Department of Obstetrics and Gynecology, University Hospital of Tromsø, Norway and followed for pregnancy outcome, 87 women had given birth (after 24th week) four to nine years after treatment. Sixty-five women had undergone conization and 22 women had been treated with vaporization. For each delivery, two controls matched for parity, age (+/- 3 years) and place of delivery were identified. The material was analyzed as a matched cohort study., Results: A strong relationship was found between conization and low birth weight. Mean birth weight after conization was 3185 g vs 3473 g,in the control women (p=0.03). Thirteen (20%) infants from women subject to conization had birth weight less than 2500 g. Relative risk of birth weight<2500 g was 2.2 (1.04-4.5) after conization, for<2000 g and< 1500 g the risk was 3.5 (1.02-12.0) and 10.0 (1.2-85.6), respectively. Four women (6.2%) with normal deliveries prior to conization experienced one or several stillbirths after treatment. No difference in birth weight was observed for women after vaporization compared to their controls., Conclusion: Excisional surgery on the cervix increases the risk for low birth weight in subsequent pregnancies. Pregnant women with prior conization need careful antenatal care.

Study Objective: To determine the influence of children born to immigrant mothers on the total proportions of low birth weight and preterm deliveries in Oslo and to explain the increases in the proportions of children with low birth weight and low gestational age since 1980-1982., Design: This was a cross sectional study based on Norwegian Medical Birth Registry data and information on mothers' country of birth from the Central Bureau of Statistics., Setting: Oslo, Norway 1968-91., Population: All births in Oslo between 1968 and 1991 (n = 146 133)., Main Results: The observed increased proportion of children with low birth weight and low gestational age born after 1980-82 is not the result of an increased proportion of children born to immigrant women. Caesarean section rates have increased dramatically and the higher proportions of children with low birth weight and gestational age may be explained by this., Conclusion: Wide use of caesarean section probably results in more children of low birth weight and low gestational age as an iatrogenic effect. The trend in the proportion of children with low birth weight and low gestational age is not correlated to perinatal mortality after 1982. Using proportions of low birth weight and gestational age as indicators of a nation's child health status may therefore be misleading in countries with high rates of caesarean section.

Objective: To compare perinatal mortality in the United States and Norway, using a new analytic approach based on relative birth weight., Design: Comparison of linked birth and perinatal death records for US and Norwegian births from 1986 through 1987, the most recently available 2-year period., Setting: Norway and the United States., Participants: A total of 7,445,914 US births and 105,084 Norwegian births., Interventions: None., Main Outcome Measure: Perinatal weight-specific mortality after adjustment for each country's own mean birth weight., Results: The higher rate of perinatal death in the United States compared with Norway is due to an excess of preterm deliveries in the United States. Low-weight, preterm births comprise 2.9% of US births compared with 2.1% of Norwegian births. If the United States could eliminate this slight excess of preterm delivery, perinatal mortality in the United States would decrease to the level in Norway. Unexpectedly, the survival of newborns at any given birth weight is virtually the same in the United States and Norway when newborns' birth weights are considered relative to their own nation's mean weight., Conclusions: Low rates of perinatal mortality in the Scandinavian countries have usually been attributed to the heavier weights of their newborns. Higher mortality among US infants is in fact due entirely to a small excess of preterm deliveries. The lighter weights of US newborns at term appear not to affect perinatal survival. Furthermore, the apparent survival advantage of low-weight US newborns (used by policymakers as evidence of superior US intensive neonatal care) may be at least partly an artifact. When weight-specific mortality rates are adjusted to relative birth weight, low-weight newborns have the same survival in Norway as in the United States. The prevention of excess mortality among US infants depends on the prevention of preterm births, not on changes in mean birth weight.

At low birth weight the variance of last menstrual period based gestational age is wide and the distribution is positively skewed toward higher values. In this study the variance of gestational age decreases rapidly as birth weight increases, skewness decreases and kurtosis increases in approaching the mean of the birth weight distribution. Some of the wider variance and positive skewness of gestational age at low birth weight appears to reflect heterogeneity of intrauterine growth, in which infants with high values of gestational age are growth retarded. We show by partitioning each birth weight group into two groups of infants with different gestational age distributions, that at low birth weight, infants with low gestational ages have higher neonatal mortality rates but lower fetal mortality rates than infants with a higher gestational age for birth weight. The differences in mortality described between small infants at different gestational ages suggest that infants with a high LMP-based gestational age have experienced a slower rate of intrauterine growth. Some authors interpret the distributional characteristics as indications of systematic error in last menstrual period based assessment of gestational age. It appears from this study that the extent of systematic error in the estimation of LMP based gestational age may have been overstated in the past.

The aim of the present study was to evaluate whether increased resources led to a higher rate of survival among infants with a birth weight less than or equal to 1,500 g, admitted to our department during the period 1983-88. During this period both personnel and equipment were upgraded. The number of patients more than doubled from 1983-84 to 1987-88 (37 versus 89). In spite of a significant decrease in gestational age from the first to the last period (29.6 weeks versus 28.2 weeks), the total mortality rate was halved, from 40.5% in 1983-84 to 22.5% in 1987-88. There was no significant increase in disability rate among survivors. The larger increasing number of disabled children was accounted for mainly by mild spastic diplegias.

The mean birth weight of the 1,568 probands with clefts who were born in Finland between 1975 and 1985 was 3,346 g, which is lower than the mean of all live born babies in 1980 (3,541 g). The 345 who had an associated anomaly or syndrome had a mean birth weight of 3,027 g and placental weight of 538 g, compared with 3,435 g and 609 g, respectively, for those with solitary clefts. The more severe the cleft the lower the birth weight, but not the placental weight. The percentage of low birthweight (less than or equal to 2,500 g) infants was higher than in the general population (8.5% compared with 3.8%). The highest percentage of low birthweight infants was in the subgroup with bilateral cleft lip and palate (16.8%).