Search

Evidence suggests that low concentrations of 25-hydroxyvitamin D(3) (25OHD3) during gestation may be associated with a range of adverse health outcomes in later life. Retrospective estimation of perinatal vitamin D status using questionnaires is extremely unreliable and stored serum samples are rarely available. We aimed to validate the use of dried blood spots (DBS) to estimate perinatal vitamin D status and to determine whether inter-group differences in cord serum 25OHD3 are reflected in DBS. We examined 25OHD3 in 4-year-old frozen cord sera and matched DBS from neonates born at a hospital in Melbourne, Australia (n = 100). We examined the correlation between these values and also investigated whether the expected seasonal (winter/spring vs. summer/autumn) difference in serum 25OHD3 was reflected in DBS values. 25OHD3 was assayed in triplicate using tandem mass spectroscopy in both a 3 microL sample of cord serum and in matched 3 mm punches from archived DBS. 25OHD3 concentrations in neonatal cord serum and DBS were highly correlated (r = 0.85, P < 0.0001). As expected, serum 25OHD3 concentrations were higher in neonates born in summer/autumn (December to March) vs. winter/spring (April to November) (median 46.6 vs. 23.7 nmol/L, P < 0.0001). A comparable difference was seen in DBS values (17.8 vs. 10.5 nmol/L, P = 0.0001). Archived DBS samples provided a valid measure of perinatal vitamin D status and identified inter-seasonal differences in perinatal 25OHD3 concentrations. They could be used for case-control studies investigating the association between perinatal vitamin D status and later health outcomes. [ABSTRACT FROM AUTHOR]

There is evidence from singletons that maternal birthweight is positively related to offspring gestational length and birthweight, and some evidence of an inverse relationship with preterm birth. Among twins very preterm birth is the major cause of neonatal mortality and of immediate and later morbidity, including neurodevelopmental impairment. We hypothesised that the relationship between maternal birthweight and gestational length would be more evident in twin than in singleton pregnancies, as there is more variation in gestation in the former. Among 131 singleton mothers carrying twins, there was weak evidence of a positive relationship between maternal birthweight and twin gestational length (+0.6 weeks [95% CI −0.05, +1.3] per kg increase in maternal birthweight, but stronger evidence among 56 of these who went into labour spontaneously (+1.9 weeks [+0.7, +3.1], P = 0.003 for interaction). In the latter group we estimated that the odds of very preterm birth (at <32 weeks) were reduced by 50% [95% CI 10%, 82%] per 250 g increase in maternal birthweight. In the whole cohort, and in this subgroup, maternal birthweight was strongly positively related to both twin offspring total birthweight and total placental weight. Our data, consistent with intergenerational programming of early development, suggest the possibility of a stronger and more clinically relevant association among twins than among singletons. Nevertheless, our sample size was modest and this finding needs to be confirmed in a larger cohort. [ABSTRACT FROM AUTHOR]

There has been much interest in evidence that people with lower birthweight have higher risk of adult cardiovascular disease, but the causal pathways underlying such observations are uncertain. Study of twins offers an opportunity to shed light on the underlying causal pathways, in particular by investigating the role of‘shared’ factors vs. factors affecting each individual fetus. This involves comparing results ofwithin-cohortvs.within-pairanalyses.Twins share many factors during gestation but birthweight discordance (difference in birthweight within a twin pair) cannot be determined by these shared factors and must relate to factors affecting growth of each individual fetus. If associations seen in a cohort of twins remain in within-pair analyses, then factors specific to each individual must be involved in the underlying causal pathways. Conversely, if the relationships disappear or substantially diminish in within-pair analyses, then factors common to the pair must be involved. Comparison of findings in monozygotic vs. dizygotic twins may provide insights into the role of genetic factors, although issues related to chorionicity need to be taken into account.We tabulate published data and conclude that differences in methodology and analyses preclude informative meta-analysis, and that analysis of pooled data would provide more useful information. [ABSTRACT FROM AUTHOR]

A number of recent studies have used data from twins to shed light on the causal pathways underlying the observed association between birthweight and cardiovascular risk factors or coronary heart disease. The issue of whether findings from twin studies are generally informative, or whether factors associated with twinning preclude generalisation, is considered here. It is concluded that the association between birthweight and later health may differ quantitatively between twins and singletons, but evidence regarding blood pressure suggests it may not differ qualitatively. However, more information is needed on a number of gestational and maternal factors, and on measures of health other than blood pressure. Placentation and issues relating to infertility and its treatment need to be recorded and, together with gestation length, may need to be taken into account in analyses. [ABSTRACT FROM AUTHOR]

Epidemiological evidence suggesting that subjects with lower birthweight have an increased risk of adult cardiovascular disease has led to increased interest in factors influencing birthweight. We have documented large changes in mean birthweight over a relatively short historical period from 1857 to 1883. Mean birthweight declined progressively from 7.9 lb (3.6 kg) in the period 1857-63 to 6.9 lb (3.1 kg) in 1874-78, then rose to 7.5 lb (3.4 kg) for the period 1879-83. We found the expected relationships between infant birthweight and maternal age, parity and marital status, and identified an association between birthweight and maternal country of birth. However, neither temporal changes in recorded maternal characteristics nor external economic indicators for the colony explained the trends in birthweight. From historical information, we believe that the explanation for our findings lies primarily with the increasing poverty, disease, mental illness, alcohol abuse and criminal activity among women admitted to the hospital between 1860 and the mid-1870s, and improvements from around 1880, when old housing was replaced and prostitutes were moved out of the area. Our findings highlight the difficulty of capturing lifestyle factors using routinely collected data, and the need for historical expertise when examining historical data. [ABSTRACT FROM AUTHOR]

There is much evidence of a link between low birthweight and elevated risk of adult cardiovascular disease, from humans and experimental animals. However, if one relies on data linking birthweight to coronary heart disease to estimate the public health implications of this association, the effects are likely to be modest. The focus on birthweight may be misplaced, because reduced size at birth may not be in the causal pathway linking gestational factors to disease in adult offspring. We need to know more about this before we can estimate the public health implications of gestational factors and assess the potential for intervention. The most studied gestational factor is maternal nutrition. We review here evidence for and against birthweight being in the causal pathways between suboptimal maternal nutrition and increased risk of adult disease in the offspring and provide evidence suggesting that birthweight is not in all of them. From a public health point of view, we suggest that future research in this field should focus on modifiable gestational exposures that may be linked to adult disease, whether or not they influence size at birth. [ABSTRACT FROM AUTHOR]