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We present three considerations in analysing the association between weight and mortality, as well as other relations that might be non-linear in nature. First, authors must graphically plot their independent and dependent variables in a continuous manner. Second, authors should assess the shape of that relation, and note its shape. If it is non-linear, and specifically, J-shaped or U-shaped, careful consideration should be given to using the 'best' statistical model, of which multivariate fractional polynomial regression is a reasonable choice. Authors should also refrain from truncating their data to avoid dealing with non-linear relations., (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.)

Purpose: Measuring ethnicity accurately is important for identifying ethnicity variations in disease risk. We evaluated the degree of agreement and accuracy of maternal ethnicity measured using the new standardized closed-ended geographically based ethnicity question and geographic reclassification of open-ended ethnicity questions from the Canadian census., Methods: A prospectively designed study of respondent agreement of mothers of healthy children aged 1-5 years recruited through the TARGet Kids! practice-based research network. For the primary analysis, the degree of agreement between geographic reclassification of the Canadian census maternal ethnicity variables and the new geographically based closed-ended maternal ethnicity variable completed by the same respondent was evaluated using a kappa analysis., Results: Eight hundred sixty-two mothers who completed both measures of ethnicity were included in the analysis. The kappa agreement statistic for the two definitions of maternal ethnicity was 0.87 (95% confidence interval, 0.84-0.90) indicating good agreement. Overall accuracy of the measurement was 93%. Sensitivity and specificity ranged from 83% to 100% and 96% to 100%, respectively., Conclusions: The new standardized closed-ended geographically based ethnicity question represents a practical alternative to widely used open-ended ethnicity questions. It may reduce risk of misinterpretation of ethnicity by respondents, simplify analysis, and improve the accuracy of ethnicity measurement., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Smoking during pregnancy has been declining in the past decades in high-income countries, including Sweden. Paradoxically, increasing trends associated with duration of residence have been reported among immigrants. We aimed to clarify how these two contrasting trends have shaped smoking patterns among immigrants., Methods: We conducted a population-based study of 1 598 433 pregnancies in Sweden in the period 1992-2008. We used multinomial logistic regression to estimate the odds of mild and heavy smoking relative to no smoking associated with year of delivery, years since migration, maternal region of birth and their interaction, after controlling for potential confounders., Results: The prevalence of smoking decreased for the Swedish-born and for immigrants during the study period. Among immigrants, duration of residence was independently associated with increases in smoking and varied according to maternal region of birth (P-value for interaction <0.001). The odds ratio associated with a 10-year increase in duration of residence was weakest for mild smoking among former Yugoslav women (adjusted odds ratio; 95% confidence interval: 1.10; 1.04-1.17) and those from other Nordic countries (1.22; 1.17-1.26) and strongest for heavy smoking among East African (4.46; 3.23-6.16) and sub-Saharan African (3.56; 2.68-4.72) women. The association between duration of residence and smoking was attenuated after stratifying by cohorts of arrival among European but not among non-European immigrants., Conclusions: Declines in smoking during pregnancy among immigrants from various regions of the world were differentially affected by opposite increasing trends throughout their residence in Sweden.

Objective: Maternal obesity is a strong risk factor for gestational diabetes mellitus and fetal macrosomia. We assessed the association between maternal visceral adiposity tissue (VAT) depth in the first half of pregnancy and both glucose tolerance in late pregnancy and newborn weight in pregnant adolescents., Methods: We completed a prospective cohort study of 73 pregnant adolescents aged 10 to 19 years, without pre-pregnancy diabetes. VAT depth was measured by ultrasound at 12 to 20 weeks' gestation, followed by a two-hour 75-g oral glucose tolerance test at 36 to 39 weeks' gestation, to determine the glucose area under the curve (AUC glucose0-120). The association between VAT depth and newborn weight was evaluated by multiple linear regression analysis, controlling for maternal age, parity, smoking, gestational age at delivery, infant sex, pre-pregnancy BMI, weight gain in pregnancy, and fasting serum glucose at 36 to 39 weeks' gestation. The relation between VAT depth and AUC glucose0-120 was assessed by linear regression analysis, adjusting for maternal age, parity, smoking, pre-pregnancy BMI, and weight gain in pregnancy., Results: A 1 cm increase in VAT depth was associated with a 206 g (95% CI 101 to 311) adjusted increase in mean birth weight. VAT depth and the other model covariates together explained more of the variance in birth weight (r(2) = 0.282; P < 0.001) than pre-pregnancy BMI with the other covariates in the same model (r(2) = 0.081; P = 0.076). All three glucose tolerance test measures were performed at 36 to 39 weeks' gestation in 51 of the 73 participants. The relationship between VAT depth and AUC glucose0-120 was not significant (P = 0.43)., Conclusion: VAT depth in the first half of pregnancy predicts newborn weight better than BMI, but is not associated with glucose tolerance in late pregnancy.

Objectives: To examine the socioeconomic gradients in birth outcomes among singleton infants in Argentina, 2003-2007., Methods: We analyzed data of 3,230,031 singleton infants born in 2003-2007, obtained from vital statistics. Associations between birth outcomes [small for gestational age (SGA), low birth weight (LBW), and preterm birth (PTB)] and socioeconomic indicators (maternal education and area-based material deprivation quintiles) were assessed with logistic regression., Results: The risk of SGA increased with higher socioeconomic disadvantage, but that of PTB decreased. Compared to mothers who attained a tertiary or university degree, mothers who did not complete primary school were more likely to have a SGA infant [adjusted OR (95 % CI): 1.65 (1.62, 1.68)], but less likely to deliver preterm [0.92 (0.90, 0.94)]. As a result of the conflicting trends in SGA and PTB, LBW exhibited inconsistent socioeconomic gradients., Conclusions: The excess risk of adverse birth outcomes associated with socioeconomic disadvantage was consistently reflected by SGA, but not by LBW and PTB. These findings challenge the usefulness of LBW as an indicator population health. Further research is needed to explain the reverse socioeconomic gradients in PTB.

Background: Newborn weight may vary between ethnic groups, but it is not known if birthweight differences exist between term babies born to immigrant mothers compared with those born in their corresponding native countries., Methods: We completed a systematic review of all birthweight curves published between 1980 and 2012, based on at least 100 singleton deliveries. We compared the 10th, 50th and 90th percentile birthweight values at 40 weeks gestation for male and female infants born in their native country vs. those infants born to mothers who had emigrated from their native country to Ontario, Canada. For the 50th percentile values, we also calculated a standardised pooled weighted difference and 95% confidence interval [CI] for both sexes. We also assessed whether birthweight differed over time, or if the differences varied by the Human Development Index (HDI) value for the native country., Results: A total of 31 studies from 21 different countries met the inclusion criteria, comprising 13 317 578 males and 12 859 119 females born at 40 weeks gestation. There was a small non-significant rise in reported birthweight percentile values between 1983 and 2006. Nearly all infants born to women in their native country had lower birthweights than those born to mothers who had emigrated from the same country to Canada at the 10th, 50th and 90th percentiles. Overall, the 50th percentile weights differed by 115 g [95% CI 74, 156] for males and 122 g [95% CI 95, 150] for females. As HDI or median birthweight increased, birthweight differences were less pronounced, but not significantly so., Conclusions: Term birthweight percentiles are typically higher among term infants born to mother who immigrate to Canada than those of infants born in their respective native country., (© 2013 Blackwell Publishing Ltd.)

Objectives: We examined the joint associations of marital status and duration of cohabitation on self-reported intimate partner violence, substance use, and postpartum depression among childbearing women., Methods: We analyzed data from the 2006-2007 Canadian Maternity Experiences Survey, a cross-sectional nationwide sample of 6421 childbearing women. Cohabiting women were married or nonmarried women living with a partner; noncohabiters were single, divorced, or separated women. We further categorized cohabiters by their duration of cohabitation (≤ 2, 3-5, or > 5 years). We used logistic regression to generate adjusted odds ratios and 95% confidence intervals., Results: About 92% of women were cohabiters. Compared with married women living with a husband more than 5 years, unmarried women cohabiting for 2 years or less were at higher odds of intimate partner violence (adjusted odds ratio [AOR] = 4.64; 95% confidence interval [CI] = 2.85, 7.56), substance use (AOR = 5.36; 95% CI = 3.06, 9.39), and postpartum depression (AOR = 1.87; 95% CI = 1.25, 2.80); these risk estimates declined with duration of cohabitation., Conclusions: Research on maternal and child health would benefit from distinguishing between married and unmarried cohabiting women, and their duration of cohabitation.

Background: Concurrent admission of a mother and her newborn to separate intensive care units (herein referred to as co-ICU admission), possibly in different centres, can magnify family discord and stress. We examined the prevalence and predictors of mother-infant separation and mortality associated with co-ICU admissions., Methods: We completed a population-based study of all 1 023 978 singleton live births in Ontario between Apr. 1, 2002, and Mar. 31, 2010. We included data for maternal-infant pairs that had co-ICU admission (n = 1216), maternal ICU admission only (n = 897), neonatal ICU (NICU) admission only (n = 123 236) or no ICU admission (n = 898 629). The primary outcome measure was mother-infant separation because of interfacility transfer., Results: The prevalence of co-ICU admissions was 1.2 per 1000 live births and was higher than maternal ICU admissions (0.9 per 1000). Maternal-newborn separation due to interfacility transfer was 30.8 (95% confidence interval [CI] 26.9-35.3) times more common in the co-ICU group than in the no-ICU group and exceeded the prevalence in the maternal ICU group and NICU group. Short-term infant mortality (< 28 days after birth) was higher in the co-ICU group (18.1 per 1000 live births; maternal age-adjusted hazard ratio [HR] 27.8, 95% CI 18.2-42.6) than in the NICU group (7.6 per 1000; age-adjusted HR 11.5, 95% CI 10.4-12.7), relative to 0.7 per 1000 in the no-ICU group. Short-term maternal mortality (< 42 days after delivery) was also higher in the co-ICU group (15.6 per 1000; age-adjusted HR 328.7, 95% CI 191.2-565.2) than in the maternal ICU group (6.7 per 1000; age-adjusted HR 140.0, 95% CI 59.5-329.2) or the NICU group (0.2 per 1000; age-adjusted HR 4.6, 95% CI 2.8-7.4)., Interpretation: Mother-infant pairs in the co-ICU group had the highest prevalence of separation due to interfacility transfer and the highest mortality compared with those in the maternal ICU and NICU groups.

Objective: The objective of the study was to compare risk factors for postpartum depression among women exposed vs not exposed to intimate partner violence and to assess the timing of abuse in relation to postpartum depression., Study Design: This was a retrospective cohort study utilizing data from the Canadian Maternity Experiences Survey, a telephone survey at 5-10 months postpartum. Survey questions were adapted from the Canadian Violence Against Women Survey and the Edinburgh Post-Natal Depression Scale., Results: Among abused women, younger (15-19 years), and older (35 years old and older), age was associated with postpartum depression, adjusted odds ratio (aOR, 2.29; 95% confidence interval [CI], 1.17-4.51) and (aOR, 2.33; 95% CI, 1.02-5.34) as was unemployment (aOR, 1.41; 95% CI, 1.06-1.84), foreign birth (aOR, 2.04; 95% CI, 1.35-3.09], and low income (aOR, 1.68; 95% CI, 1.25-2.25) among nonabused women. Postpartum depression was significantly associated with abuse occurring only prior to pregnancy (aOR, 3.28; 95% CI, 1.86-5.81), starting postpartum (aOR, 4.76; 95% CI, 1.41-16.02), and resuming postpartum (aOR, 3.81; 95% CI, 1.22-11.88)., Conclusion: Among pregnant women, subgroups defined by abuse exposure differ in their risk profile for postpartum depression., (Copyright © 2012 Mosby, Inc. All rights reserved.)

Birthweight and gestational age are the two most commonly used continuous variables in perinatal research. Dichotomous outcomes derived from these two variables include low birthweight, preterm birth and small for gestational age, each extensively used as perinatal and population health indicators within public health research and health surveillance systems. However, these dichotomous indicators have inherent limitations that need to be considered in the design, analysis and interpretation of epidemiological studies. In this report, we present seven caveats that may help researchers and users of epidemiological data avoid common (and not so common) pitfalls in the consideration of these indicators.

Objective: To determine the risk of stillbirth between 20 to 41 weeks gestation, at highly detailed weight percentiles, including extreme degrees of small (SGA) and large (LGA) for gestational age birth weight., Study Design: We completed a population-based study of all births in Ontario, Canada between 2002 and 2007. We included 767, 016 liveborn and 4,697 stillborn singletons delivered between 20 and 41 weeks gestation. Smoothed birthweight percentile curves were generated for males and females, combining livebirths and stillbirths. Quantile regression was used to calculate sex-specific absolute birthweight differences and 95% confidence intervals (CI) between stillborns vs liveborns at various gestational ages. Logistic regression was used to calculate the odds ratios (OR) for stillbirth at various sex-specific birthweight percentiles, including <1st and ≥ 99th percentile. OR were adjusted for maternal age and parity., Result: At the 10th percentile, stillborns weighed significantly less than liveborns starting at 24 weeks gestation. By 32 weeks, this difference was 590 g (95% CI 430 to 750) for males and 551 g (95% CI 345 to 448) for females. A reverse J-shaped association was observed between birthweight percentile and risk of stillbirth across all gestational ages. Relative to the 40th to 60th percentile referent, the adjusted OR for stillbirth was 9.63 (95% CI 8.39 to 11.06) at a birth weight <1st percentile. At ≥ 99th percentile, the adjusted OR was 2.24 (95% CI 1.76 to 2.86). The risk of stillbirth at extreme birthweight percentiles was robustly observed across gestational ages., Conclusion: Substantial birthweight differences exist between stillborns and newborns. As a possible hallmark of impending intrauterine death, severe SGA and LGA may each be potential targets for future stillbirth prevention initiatives.

Objective: To determine the likelihood that infants born to Filipina, other East Asian, and Canadian-born women may be misclassified as small for gestational age when using conventional Canadian birth weight curves rather than those specific to their world region., Methods: We conducted a population-based study of 548 418 singleton live births in Ontario between 2002 and 2007. Smoothed birth weight percentile curves were generated for males and females born to women from Canada, the Philippines, and the rest of East Asia/Pacific. We determined the likelihood of misclassifying an infant as small for gestational age (SGA < 10th percentile weight) or large for gestational age (LGA ≥ 90th percentile weight) on a Canadian-born birth weight curve vs. a curve specific to the other two world regions., Results: For gestation-specific 10th and 50th percentiles, term infants born to women from the Philippines often had significantly lower birth weights than infants of Canadian-born mothers. Controlling for maternal age and parity, approximately 88 per 1000 male newborns (95% CI 82 to 95) and 72 per 1000 female newborns (95% CI 54 to 60) of mothers from the Philippines were at risk of being misclassified as SGA. LGA would be missed in approximately 54 per 1000 male newborns (95% CI 49 to 59) and 49 per 1000 female newborns (95% CI 44 to 54) of Filipina mothers. Misclassification of both SGA and LGA was more pronounced among infants of Filipina mothers than of mothers from other East Asian origin., Conclusions: Infants of mothers born in the Philippines weigh significantly less than those of Canadian-born women or mothers emigrating from other East Asian countries. Those who use birth weight curves should consider these differences.

Objectives: We describe the prevalence of abuse before, during, and after pregnancy among a national population-based sample of Canadian new mothers., Methods: We estimated prevalence, frequency, and timing of physical and sexual abuse, identified category of perpetrator, and examined the distribution of abuse by social and demographic characteristics in a weighted sample of 76,500 (unweighted sample = 6421) Canadian mothers interviewed postpartum for the Maternity Experiences Survey (2006-2007)., Results: Prevalence of any abuse in the 2 years before the interviews was 10.9% (6% before pregnancy only, 1.4% during pregnancy only, 1% postpartum only, and 2.5% in any combination of these times). The prevalence of any abuse was higher among low-income mothers (21.2%), lone mothers (35.3%), and Aboriginal mothers (30.6%). In 52% of the cases, abuse was perpetrated by an intimate partner. Receiving information on what to do was reported by 61% of the abused mothers., Conclusions: Large population-based studies on abuse around pregnancy can facilitate the identification of patterns of abuse and women at high risk for abuse. Before and after pregnancy may be particularly important times to monitor risk of abuse.

Objectives: To examine the relationship between neighbourhood deprivation and concentration of immigrants, and abuse among immigrant women versus non-immigrant women., Methods: Using data from the Canadian Maternity Experiences Survey (un-weighted sample N = 5,679 and weighted sample N = 68,719) linked to the neighbourhoods Census data, we performed contextual analysis to compare abuse prevalence among: immigrants ≤5 years, immigrants >5 years and Canadian-born. We identified two level effect modifiers: living in high (≤15 % of households at or below low-income cut-off- [LICO]) versus low-income (>15 % below LICO) neighbourhoods and living in high (≥25 %) versus low immigrant (<25 %) neighbourhoods. Individual socioeconomic position (SEP), family variables and neighbourhood SEP or percentage of immigrants were considered in different logistic regression models., Results: Immigrant women were less likely to experience abuse even upon adjustment for individual SEP, family variables and neighbourhood characteristics. The protective effect of the neighborhood was stronger among immigrant women living in low-income and high immigrant neighborhoods, irrespective of length of stay in Canada., Conclusion: Policies and interventions to reduce abuse among immigrant women need to consider neighbourhood's SEP and concentration of immigrants.

Background: There has been much discussion about whether female feticide occurs in certain immigrant groups in Canada. We examined data on live births in Ontario and compared sex ratios in different groups according to the mother's country or region of birth and parity., Methods: We completed a population-based study of 766,688 singleton live births between 2002 and 2007. We used birth records provided by Ontario Vital Statistics for live births in the province between 23 and 41 weeks' gestation. We categorized each newborn according to the mother's country or region of birth, namely Canada (n = 486,599), Europe (n = 58,505), South Korea (n = 3663), China (n = 23,818), Philippines (n = 15,367), rest of East Asia (n = 18,971), Pakistan (n = 18,018), India (n = 31,978), rest of South Asia (n = 20,695) and other countries (n = 89,074). We calculated male:female ratios and 95% confidence intervals (CIs) for all live births by these regions and stratified them by maternal parity at the time of delivery (0, 1, 2 or ≥ 3)., Results: Among infants of nulliparous women, the male:female ratio was about 1.05 overall. As parity increased, the ratio remained unchanged among infants of Canadian-born women. In contrast, the male:female ratio was significantly higher among infants of primiparous women born in South Korea (1.20, 95% CI 1.09-1.34) and India (1.11, 95% CI 1.07-1.15) than among infants of Canadian-born primiparous women. Among multiparous women, those born in India were significantly more likely than Canadian-born women to have a male infant (parity 2, ratio 1.36, 95% CI 1.27-1.46; parity ≥ 3, ratio 1.25, 95% CI 1.09-1.43)., Interpretation: Our study of male:female ratios in Ontario showed that multiparous women born in India were significantly more likely than multiparous women born in Canada to have a male infant.

The immigrant paradox refers to the contrasting observations that immigrants usually experience similar or better health outcomes than the native-born population despite socioeconomic disadvantage and barriers to health care use. This paradox, however, has not been examined simultaneously in relation to varying degrees of exposure to the receiving society and across multiple outcomes and risk factors. To advance knowledge on these issues, we analysed data of the Maternity Experiences Survey, a nationally representative cross-sectional survey of 6421 Canadian women who delivered singleton infants in 2006-07. We compared the prevalence of adverse pregnancy outcomes and related risk factors according to women's ethnicity and time since migration to Canada. We calculated prevalences and prevalence ratios (PR) with 95% confidence intervals. Compared to Canadian-born women of European descent, recent immigrants were at lower risk of preterm delivery and morbidity during pregnancy despite having the highest prevalence of low income and low support during pregnancy among all groups, but the paradox was not observed among immigrants with a longer stay in Canada. In contrast, recent immigrants were at higher risk of postpartum depression. Immigrants of non-European origin also had higher prevalence of postpartum depression, irrespective of their length of residence in Canada, but immigrants from European-origin countries did not. Exposure to Canada was also positively associated with higher alcohol and tobacco consumption and body mass index. Canadian-born women of non-European descent were at higher risk of preterm birth and hospitalisation during pregnancy than their European-origin counterparts. Our findings suggest that the healthy migrant hypothesis and the immigrant paradox have limited generalisability. These hypotheses may be better conceptualised as outcome-specific and dependent on immigrants' ethnicity and length of stay in the receiving country., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Objective: Research conducted outside Canada suggests that preeclampsia (PET) may be more common among certain ethnic groups. A limitation to prior studies is that they did not distinguish between immigrant and non-immigrant women; they also included women with mild PET arising near term, the clinical importance of which is debatable. We created the term "serious PET" to describe a diagnosis of severe PET, eclampsia, or any degree of PET with concomitant preterm delivery, fetal death, or maternal hospitalization of seven days or more, and evaluated its risk in association with world region of origin among recent immigrants to Ontario., Methods: Using the federal Landed Immigrant Data System database (LIDS), we completed a population-based study of 118 849 women who immigrated to Ontario between 1985 and 2000. The LIDS was linked to the Canadian Institute for Health Information's Discharge Abstracts Database, thereby capturing all hospitalizations with subsequent delivery in Ontario between April 1, 2002, and March 31, 2009. Rates for serious PET were determined according to maternal world region of birth, and odds ratios were adjusted for maternal age, number of live births, multifetal pregnancy, diabetes mellitus status, level of formal education, place of residence, neighbourhood income quintile, duration of residence in Canada, and fiscal year of delivery., Results: Immigrant women from the Caribbean (6.8 per 1000; OR 3.34; 95% CI 2.25 to 4.96), Sub-Saharan Africa (6.8 per 1000; OR 3.14; 95% CI 2.04 to 4.83) and Hispanic America (5.9 per 1000; OR 3.11; 95% CI 1.97 to 4.88) were at highest risk of serious PET relative to immigrant women from industrialized nations. The ORs were either unchanged or higher when restricted to women without a prior live birth., Conclusion: We identified immigrant groups at higher risk of serious PET, whose consequences would presumably include greater financial costs for hospital care and a negative impact on maternal and newborn well-being.

Background: Newborns of certain immigrant mothers are smaller at birth than those of domestically born mothers. Contemporary, population-derived percentile curves for these newborns are lacking, as are estimates of their risk of being misclassified as too small or too large using conventional rather than tailored birth weight curves., Methods: We completed a population-based study of 766 688 singleton live births in Ontario from 2002 to 2007. Smoothed birth weight percentile curves were generated for males and females, categorized by maternal world region of birth: Canada (63.5%), Europe/Western nations (7.6%), Africa/Caribbean (4.9%), Middle East/North Africa (3.4%), Latin America (3.4%), East Asia/Pacific (8.1%), and South Asia (9.2%). We determined the likelihood of misclassifying an infant as small for gestational age (≤ 10th percentile for weight) or as large for gestational age (≥ 90th percentile for weight) on a Canadian-born maternal curve versus one specific to maternal world region of origin., Results: Significantly lower birth weights were seen at gestation-specific 10th, 50th, and 90th percentiles among term infants born to mothers from each world region, with the exception of Europe/Western nations, compared with those for infants of Canadian-born mothers. For example, for South Asian babies born at 40 weeks' gestation, the absolute difference at the 10th percentile was 198 g (95% CI 183 to 212) for males and 170 g (95% CI 161 to 179) for females. Controlling for maternal age and parity, South Asian males had an odds ratio of 2.60 (95% CI 2.53 to 2.68) of being misclassified as small for gestational age, equivalent to approximately 116 in 1000 newborns; for South Asian females the OR was 2.41 (95% CI 2.34 to 2.48), equivalent to approximately 106 per 1000 newborns. Large for gestational age would be missed in approximately 61 per 1000 male and 57 per 1000 female South Asian newborns if conventional rather than ethnicity-specific birth weight curves were used., Conclusions: Birth weight curves need to be modified for newborns of immigrant mothers originating from non-European/Western nations.

Immigrants' health is jointly influenced by their pre- and post-migration exposures, but how these two influences operate with increasing duration of residence has not been well-researched. We aimed to examine how the influence of maternal country of birth and neighborhood deprivation effects, if any, change over time since migration and how neighborhood effects among immigrants compare with those observed in the Canadian-born population. Birth data from Ontario hospital records (2002-2007) were linked with an official Canadian immigration database (1985-2000). The outcome measure was preterm birth. Neighborhoods were ranked according to a neighborhood deprivation index developed for Canadian urban areas and collapsed into tertiles of approximately equal size. Time since immigration was measured from the date of arrival to Canada to the date of delivery, ranging from 1 to 22 years. We used cross-classified random effect models to simultaneously account for the membership of births (N = 83,233) to urban neighborhoods (N = 1,801) and maternal countries of birth (N = 168). There were no differences in preterm birth between neighborhood deprivation tertiles among immigrants with less than 15 years of residence. Among immigrants with 15 years of stay or more, the adjusted absolute risk difference (ARD%, 95% confidence interval) between high-deprived (tertile 3) and low-deprived (tertile 1) neighborhoods was 1.86 (0.68, 2.98), while the ARD% observed among the Canadian-born (N = 314,237) was 1.34 (1.11, 1.57). Time since migration modifies the neighborhood deprivation gradient in preterm birth among immigrants living in Ontario cities. Immigrants reached the level of inequalities in preterm birth observed at the neighborhood level among the Canadian-born after 14 years of stay, but neighborhoods did not influence preterm birth among more recent immigrants, for whom the maternal country of birth was more predictive of preterm birth.

Background: Abuse and violence against women constitute a global public health problem and are particularly important among women of reproductive age. The literature is not conclusive regarding the impact of violence against pregnant women on adverse pregnancy outcomes, such as preterm birth, small for gestational age and postpartum depression. Most studies have been conducted on relatively small samples of high-risk women. Our objective was to investigate what dimensions of violence against pregnant women were associated with preterm birth, small for gestational age and postpartum depression in a nationally representative sample of Canadian women., Methods: We analysed data of the Maternity Experiences Survey, a nationally representative survey of Canadian women giving birth in 2006. The comprehensive questionnaire included a 19-item section to collect information on different dimensions of abuse and violence, such as type, frequency, timing and perpetrator of violence. The survey design is a stratified simple random sample from the 2006 Canadian Census sampling frame. Participants were 6,421 biological mothers (78% response rate) 15 years and older who gave birth to a singleton live birth and lived with their infant at the time of the survey. Logistic regression was used to compute Odds Ratios. Survey weights were used to obtain point estimates and 95% confidence intervals were obtained with the jacknife method of variance estimation. Covariate control was informed by use of directed acyclic graphs., Results: No statistically significant associations were found for preterm birth or small for gestational age, after adjustment. Most dimensions of violence were associated with postpartum depression, particularly the combination of threats and physical violence starting before and continuing during pregnancy (Adjusted Odds Ratio = 4.1, 95% confidence interval: 1.9, 8.9) and perpetrated by the partner (4.3: 2.1, 8.7)., Conclusions: Our findings provide weak evidence of an association between experiences of abuse before and during pregnancy and preterm birth and small for gestational age but they indicate that several dimensions of abuse and violence are consistently associated with postpartum depression.

The literature on migration and health is quite heterogeneous in how migrants are labelled and how the relation between migration and health is conceptualised. A narrative review has been carried out. This glossary presents the most commonly used terms in the field of migration and health, along with synonyms and related concepts, and discusses the suitability of their use in epidemiological studies. The terminology used in migrant health is ambiguous in many cases. Studies on migrant health should avoid layman terms and strive to use internationally defined concepts.

Objective: To develop new and improved reference birthweights for the Argentine population as a whole with a breakdown by gestational age (GA), sex and multiplicity of birth., Methods: The population studied included all live births resulting from single (n = 3,478,286) and double (n = 57,654) births in Argentina during the period 2003- 2007. The probable errors in classifying GA on the basis of last menstruation were corrected using normal mixture models. The percentiles were obtained by quantile regression, which also made it possible to smooth out the curves., Results: Birthweight curves for single births were obtained between weeks 22 and 43 of gestation, and curves for double births between weeks 24 and 41, with a breakdown by the sex of the neonate. Compared with those of previous studies, these reference birthweights do not overestimate the proportion of live births large for their GA. An increase in birthweight was also observed during the period of study., Conclusions: The proposed curves have the advantages of being based on large numbers, of being representative of the most recent Argentine births, of distinguishing the number of births and the sex of the neonates, and of minimizing GA classification errors. They are therefore a useful tool for measuring inequalities and thus identifying population groups at higher risk of adverse perinatal events.

Research on the health status of international migrants to industrialised countries in general, and on perinatal outcomes in particular, has assumed an interpretative model based on primary migration, characterised by one permanent cross-border movement from the migrant's country of birth. However, many migrants experience more complex migration patterns that may also be associated with human health. Secondary migration, defined as a migration from a country of residence other than the country where the immigrant was born, has been growing during the last two decades, favoured by globalisation. The purpose of this study was to examine the association between secondary migration and preterm birth (PTB) and infant birthweight at term (BW) using a Canadian official immigration database to build a cohort of immigrants to Ontario, Canada, who obtained their permanent residence in the years 1985-2000. The study population comprised 320,398 singleton live infants born to immigrant women during 1988-2007. Primary and secondary migrants were categorised according to whether they were born in an industrialised country or not. Secondary migrants were further subdivided according to whether the country from which they migrated to Canada was industrialised or not. We found that compared to primary migrants, secondary migrants to Canada born in non-industrialised countries had lower odds of PTB and higher mean BW at term. However, such a protective effect was not observed among secondary migrants born in industrialised countries. In a cross-classified multilevel model restricted to secondary migrants, 5.2% of the variation in birthweight was explained by migrants' countries of birth and 0.8% by migrants' countries of last permanent residence. These findings are consistent with the so-called healthy migrant effect, implying that selective migration from non-industrialised countries is associated with protective individual characteristics., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Background: The association between fetal exposure to major radiodiagnostic testing in pregnancy-computed tomography (CT) and radionuclide imaging-and the risk of childhood cancer is not established., Methods and Findings: We completed a population-based study of 1.8 million maternal-child pairs in the province of Ontario, from 1991 to 2008. We used Ontario's universal health care-linked administrative databases to identify all term obstetrical deliveries and newborn records, inpatient and outpatient major radiodiagnostic services, as well as all children with a malignancy after birth. There were 5,590 mothers exposed to major radiodiagnostic testing in pregnancy (3.0 per 1,000) and 1,829,927 mothers not exposed. The rate of radiodiagnostic testing increased from 1.1 to 6.3 per 1,000 pregnancies over the study period; about 73% of tests were CT scans. After a median duration of follow-up of 8.9 years, four childhood cancers arose in the exposed group (1.13 per 10,000 person-years) and 2,539 cancers in the unexposed group (1.56 per 10,000 person-years), a crude hazard ratio of 0.69 (95% confidence interval 0.26-1.82). After adjusting for maternal age, income quintile, urban status, and maternal cancer, as well as infant sex, chromosomal or congenital anomalies, and major radiodiagnostic test exposure after birth, the risk was essentially unchanged (hazard ratio 0.68, 95% confidence interval 0.25-1.80)., Conclusions: Although major radiodiagnostic testing is now performed in about 1 in 160 pregnancies in Ontario, the absolute annual risk of childhood malignancy following exposure in utero remains about 1 in 10,000. Since the upper confidence limit of the relative risk of malignancy may be as high as 1.8 times that of an unexposed pregnancy, we cannot exclude the possibility that fetal exposure to CT or radionuclide imaging is carcinogenic.

Objective: This study aimed to examine preterm and small-for-gestational-age (SGA) births among immigrants, by duration of residence, and to compare them with the Canadian-born population., Design: Population-based cross-sectional study with retrospective assessment of immigration., Setting: Metropolitan areas of Ontario, Canada., Population: A total of 83 233 singleton newborns born to immigrant mothers and 314 237 newborns born to non-immigrant mothers., Methods: We linked a database of immigrants acquiring permanent residence in Ontario, Canada, in the period 1985-2000 with mother-infant hospital records (2002-2007). Duration of residence was measured as completed years from arrival to Canada to delivery/birth. Logistic regression models were used to estimate the effects of duration of residence with adjusted odds ratios and 95% confidence intervals. In analyses restricted to immigrants only, hierarchical models were used to account for the clustering of births into maternal countries of birth., Main Outcome Measures: Preterm birth (PTB) and SGA birth., Results: Recent immigrants (<5 years) had a lower risk of PTB (4.7%) than non-immigrants (6.2%), but those with > or =15 years of stay were at higher risk (7.4%). Among immigrants, a 5-year increase in Canadian residence was associated with an increase in PTB (AOR 1.14, 95% CI 1.10-1.19), but not in SGA birth (AOR 0.99, 95% CI 0.96-1.02)., Conclusions: Time since migration was associated with increases in the risk of PTB, but was not associated with an increase in SGA births. Ignoring duration of residence may mask important disparities in preterm delivery between immigrants and non-immigrants, and between immigrant subgroups categorised by their duration of residence.

Objectives: We compared the influence of the residential environment and maternal country of origin on birthweight and low birthweight of infants born to recent immigrants to urban Ontario., Methods: We linked delivery records (1993-2000) to an immigration database (1993-1995) and small-area census data (1996). The data were analyzed with cross-classified random-effects models and standard multilevel methods. Higher-level predictors included 4 independent measures of neighborhood context constructed by factor analysis and maternal world regions of origin., Results: Births (N = 22 189) were distributed across 1396 census tracts and 155 countries of origin. The associations between neighborhood indices and birthweight disappeared after we controlled for the maternal country of origin in a cross-classified multilevel model. Significant associations between world regions and birthweight and low birthweight persisted after we controlled for neighborhood context and individual characteristics., Conclusions: The residential environment has little, if any, influence on birthweight among recent immigrants to Ontario. Country of origin appears to be a much more important factor in low birthweight among children of recent immigrants than current neighborhood. Findings of neighborhood influences among recent immigrants should be interpreted with caution.

Objectives: This article examines differences in birth outcomes by neighbourhood income and recent immigration for singleton live births in Toronto, Ontario., Data Sources: The birth data were extracted from hospital discharge abstracts compiled by the Canadian Institute for Health Information., Analytical Techniques: A population-based cross-sectional study of 143,030 singleton live births to mothers residing in Toronto, Ontario from 1 April 1996 through 31 March 2001 was conducted. Neighbourhood income quintiles of births were constructed after ranking census tracts according to the proportion of their population below Statistics Canada's low-income cutoffs. Logistic regression was used to estimate odds ratios for the effects of neighbourhood income quintile and recent immigration on preterm birth, low birthweight and full-term low birthweight, adjusted for infant sex and maternal age., Main Results: Low neighbourhood income was associated with a moderately higher risk of preterm birth, low birthweight, and full-term low birthweight. The neighbourhood income gradient was less pronounced among recent immigrants compared with longer-term residents. Recent immigration was associated with a lower risk of preterm birth, but a higher risk of low birthweight and full-term low birthweight.

This study aimed to examine differences in multiple maternities by neighborhood-income levels in Toronto, Canada. Hospital records were used to perform secondary analysis of 144,731 maternities resulting in single or multiple infants live-born to mothers residing in the City of Toronto 1996 to 2001. The independent variable was neighborhood income, defined as mean household neighborhoodincome quintiles. Multiple logistic regression analysis was used to compute adjusted odds ratios (AORs) and 95% confidence intervals (CIs). Differences by income levels were found in twin maternities but not in higher order maternities. Twin maternities were more likely to occur in the richest neighborhood-income quintile compared to the rest of the population (AOR: 1.25, 95% CI: 1.10-1.41), after adjustment for potential confounders. The positive association between high neighborhood income and twin maternities found in this study suggests that the richest neighborhoods select families whose characteristics pose them at increased risk of having twins. Further studies are needed to clarify the underlying mechanisms leading to socioeconomic differences in multiple births.