Alison L. Park

Association between maternal comorbidity and preterm birth by severity and clinical subtype: retrospective cohort study.

BackgroundPreterm birth (PTB) is a major cause of infant morbidity and mortality, but the relationship between comorbidity and PTB by clinical subtype and severity of gestational age remains poorly understood. We evaluated associations between maternal comorbidities and PTB by clinical subtype and gestational age.MethodsWe conducted a retrospective cohort study of 1,329,737 singleton births delivered in hospitals in the province of Québec, Canada, 1989-2006. PTB was classified by clinical subtype (medically indicated, preterm premature rupture of membranes (PPROM), spontaneous preterm labour) and gestational age (< 28, 28-31, 32-36 completed weeks). Odds ratios (OR) of PTB by clinical subtype for systemic and localized maternal comorbidities were estimated using polytomous logistic regression, adjusting for maternal age, grand multiparity, and period. Attributable fractions were calculated.ResultsPTB rates were higher among mothers with comorbidity (10.9%) compared to those without comorbidity (4.7%). Several comorbidities were associated with greater odds of medically indicated PTB compared with no comorbidity, but only comorbidities localized to the reproductive system were associated with spontaneous PTB. Drug dependence and mental disorders were strongly associated with PPROM and spontaneous PTBs across all gestational ages (OR > 2.0). At the population level, several major comorbidities (placental abruption, chorioamnionitis, oliogohydramnios, structural abnormality, cervical incompetence) were key contributors to all clinical subtypes of PTB, especially at < 32 weeks. Major systemic comorbidities (preeclampsia, anemia) were key contributors to PPROM and medically indicated PTBs.ConclusionsThe relationship between comorbidity and clinical subtypes of PTB depends on gestational age. Prevention of PPROM and spontaneous PTB may benefit from greater attention to preeclampsia, anemia and comorbidities localized to the reproductive system.

Weighing the contributions of material and social area deprivation to preterm birth

Evidence suggests that individual socioeconomic status is a better predictor of preterm birth (PTB) than other individual social characteristics, but it is not clear if socioeconomic (material) area context is likewise more strongly related to PTB than social area characteristics. We compared material and social area deprivation to determine which was more strongly associated with PTB. Live singleton births from Québec, Canada were obtained for 1999-2006 (N = 581,898). PTB was defined as <37 completed gestational weeks. Two composite indices representing area-level material and social deprivation were used in Cox proportional hazards regression models to compute hazard ratios (HR) and 95% confidence intervals (CI) for PTB, accounting for individual-level characteristics including maternal education. Results indicated that PTB rates were higher for areas with high material (7.1%) and social (6.8%) deprivation than those with low material (5.5%) and social (5.9%) deprivation. Adjusted hazards of PTB were slightly greater for material deprivation than social deprivation. These findings indicate that material area deprivation is marginally more strongly associated with PTB than social deprivation, but it is not clear that interventions to prevent PTB should focus on material deprivation any more than on social area deprivation.

Rates of stillbirth by gestational age and cause in Inuit and First Nations populations in Quebec

Background: Inuit and First Nations populations have higher rates of stillbirth than non-Aboriginal populations in Canada do, but little is known about the timing and cause of stillbirth in Aboriginal populations. We compared gestational age– and cause-specific stillbirth rates in Inuit and First Nations populations with the rates in the non-Aboriginal population in Quebec. Methods: Data included singleton stillbirths and live births at 24 or more gestational weeks among Quebec residents from 1981 to 2009. We calculated odds ratios (ORs), rate differences and 95% confidence intervals (CIs) for the retrospective cohort of Inuit and First Nations births relative to non-Aboriginal births using fetuses at risk (i.e., ongoing pregnancies) as denominators and adjusting for maternal characteristics. The main outcomes were stillbirth by gestational age (24–27, 28–36, ≥ 37 wk) and cause of death. Results: Rates of stillbirth per 1000 births were greater among Inuit (6.8) and First Nations (5.7) than among non-Aboriginal (3.6) residents. Relative to the non-Aboriginal population, the risk of stillbirth was greater at term (≥ 37 wk) than before term for both Inuit (OR 3.1, 95% CI 1.9 to 4.8) and First Nations (OR 2.6, 95% CI 2.1 to 3.3) populations. Causes most strongly associated with stillbirth were poor fetal growth, placental disorders and congenital anomalies among the Inuit, and hypertension and diabetes among the First Nations residents. Interpretation: Stillbirth rates in Aboriginal populations were particularly high at term gestation. Poor fetal growth, placental disorders and congenital anomalies were important causes of stillbirth among the Inuit, and diabetic and hypertensive complications were important causes in the First Nations population. Prevention may require improvements in pregnancy and obstetric care.

Extreme maternal education and preterm birth: time-to-event analysis of age and nativity-dependent risks

PURPOSE Increasing numbers of women achieve extremely high education, but the association with preterm birth (PTB) is poorly understood, especially over the life course. We sought to determine how very high educational attainment is associated with PTB, and to assess differences by maternal age and nativity. METHODS Data included singleton live births to mothers aged ≥ 20 years in metropolitan areas of Québec, Canada, from 1995 to 2005 (n = 537,525). Hazard ratios of PTB (<37 gestational weeks) were estimated over the continuous range of education (0-30 years) according to maternal age (20-24, 25-29, 30-34, ≥ 35 years) and nativity in a flexible survival model. RESULTS The relationship between education and PTB was not linear, but suggested that extremely high education was not as protective against PTB as slightly lower education. Education thresholds that offered maximum protection increased with maternal age, and were lower for Canadian-born (17-21 years of education) than foreign-born (22-25 years of education) mothers. CONCLUSIONS Extremely high education did not confer more protection against PTB than slightly lower education, and associations varied over the life course. The threshold number of years of education most protective against PTB: (1) increased with maternal age, especially for Canadian-born mothers, and (2) was higher for foreign-born mothers.

Educational Inequalities in Preterm and Term Small-for-Gestational-Age Birth Over Time

PURPOSE Time trends in educational inequalities in small-for-gestational-age (SGA) birth are important to evaluate for policy, especially at preterm gestational ages when morbidity and mortality are typically greater. We evaluated educational inequalities in preterm and term SGA birth over time, accounting for potential bias at preterm gestational ages. METHODS Data included 2,204,056 singleton live births from 25 to 43 gestational weeks, 1981 to 2007. We estimated prevalence ratios (PR) and percent prevalence differences (PPD) of preterm and term SGA birth for a continuous education score, accounting for maternal characteristics. Sensitivity analyses included correction for misclassification of preterm SGA status, and use of fetuses-at-risk denominators in regression models. RESULTS Although prevalence of SGA birth decreased over time, relative educational inequalities (PRs) persisted for preterm and term cases. PPDs decreased slightly, but more for term than preterm SGA birth. Sensitivity analyses indicated that PRs for education were stronger for preterm than term SGA birth. PPDs were larger for term SGA birth in the first period, but greater for preterm SGA birth in the last period. CONCLUSIONS Relative educational inequalities in SGA birth persisted over time. The difference in prevalence between the least and most educated mothers is currently greater for preterm than for term SGA birth.

Preterm birth in the Inuit and First Nations populations of Québec, Canada, 1981-2008

Objectives: To evaluate preterm birth (PTB) for Inuit and First Nations vs. non-Indigenous populations in the province of Québec, Canada. Study design: Retrospective cohort study. Methods: We evaluated singleton live births for Québec residents, 1981–2008 (n = 2,310,466). Municipality of residence (Inuit-inhabited, First Nations-inhabited, rest of Québec) and language (Inuit, First Nations, French/English) were used to identify Inuit and First Nations births. The outcome was PTB (<37 completed weeks). Cox proportional hazards regression was employed to estimate hazard ratios (HR) and 95% confidence intervals (CI) of PTB, adjusting for maternal age, education, marital status, parity and birth year. Results: PTB rates were higher for Inuit language speakers in Inuit-inhabited areas and the rest of Québec compared with French/English speakers in the rest of Québec, and disparities persisted over time. Relative to French/English speakers in the rest of Québec, Inuit language speakers in the rest of Québec had the highest risk of PTB (HR 1.98, 95% CI: 1.62–2.41). The risk was also elevated for Inuit language speakers in Inuit-inhabited areas, though to a lesser extent (HR 1.29, 95% CI: 1.18–1.41). In contrast, First Nations language speakers in First Nations-inhabited areas and the rest of Québec had similar or lower risks of PTB relative to French/English speakers in the rest of Québec. Conclusions: Inuit populations, especially those outside Inuit-inhabited areas, have persistently elevated risks of PTB, indicating a need for strategies to prevent PTB in this population.OBJECTIVES To evaluate preterm birth (PTB) for Inuit and First Nations vs. non-Indigenous populations in the province of Québec, Canada. STUDY DESIGN Retrospective cohort study. METHODS We evaluated singleton live births for Québec residents, 1981-2008 (n = 2,310,466). Municipality of residence (Inuit-inhabited, First Nations-inhabited, rest of Québec) and language (Inuit, First Nations, French/English) were used to identify Inuit and First Nations births. The outcome was PTB (<37 completed weeks). Cox proportional hazards regression was employed to estimate hazard ratios (HR) and 95% confidence intervals (CI) of PTB, adjusting for maternal age, education, marital status, parity and birth year. RESULTS PTB rates were higher for Inuit language speakers in Inuit-inhabited areas and the rest of Québec compared with French/English speakers in the rest of Québec, and disparities persisted over time. Relative to French/English speakers in the rest of Québec, Inuit language speakers in the rest of Québec had the highest risk of PTB (HR 1.98, 95% CI: 1.62-2.41). The risk was also elevated for Inuit language speakers in Inuit-inhabited areas, though to a lesser extent (HR 1.29, 95% CI: 1.18-1.41). In contrast, First Nations language speakers in First Nations-inhabited areas and the rest of Québec had similar or lower risks of PTB relative to French/English speakers in the rest of Québec. CONCLUSIONS Inuit populations, especially those outside Inuit-inhabited areas, have persistently elevated risks of PTB, indicating a need for strategies to prevent PTB in this population.

Contribution of local area deprivation to cultural-linguistic inequalities in foetal growth restriction: Trends over time in a Canadian metropolitan centre

This study investigated temporal trends in heterogeneity of foetal growth restriction across neighbourhood deprivation levels for two culturally distinct communities (Anglophones and Francophones) in a North American metropolitan centre. Inequalities in foetal growth restriction related to deprivation fell from 1989 to 2008 for Francophones, but initial improvements for Anglophones later reversed with a rise in poor foetal growth in the most materially disadvantaged and, unexpectedly, advantaged areas as well. Inequalities in foetal growth restriction related to neighbourhood material deprivation may be emerging in this minority Anglophone population. Potential mechanisms underlying these trends are discussed, as well as implications for perinatal health policy.

Widening inequality in extreme macrosomia between Indigenous and non-Indigenous populations of Québec, Canada.

Objective : To evaluate trends in macrosomia by severity in Indigenous vs. non‐Indigenous populations of Québec, Canada.