Background: Cerebral palsy (CP) has a multifactorial etiology, and placental vascular disease may be one major risk factor. The risk of placental vascular disease may be lower among some immigrant groups. We studied the association between immigrant status and the risk of CP. Methods: We conducted a population-based retrospective cohort study of all singleton and twin livebirths in Ontario between 2002-2008, and who survived ≥28 days after birth. Each child was assessed for CP up to age 4 years, based on either a single inpatient or ≥2 outpatient pediatric diagnoses of CP. Relative to non-immigrants (n = 566,668), the risk of CP was assessed for all immigrants (n = 177,390), and further evaluated by World region of origin. Cox proportional hazard ratios (aHR) were adjusted for maternal age, income, diabetes mellitus, obesity, tobacco use, Caesarean delivery, year of delivery, physician visits, twin pregnancy, preterm delivery, as well as small- and large-for-gestational age birthweight. Results: There were 1346 cases of CP, with a lower rate among immigrants (1.45 per 1000) than non-immigrants (1.92 per 1000) (aHR 0.77, 95% confidence interval [CI] 0.67 to 0.88). Mothers from East Asia and the Pacific (aHR 0.54, 95% CI 0.39 to 0.77) and the Caribbean (aHR 0.58, 95% CI 0.37 to 0.93) were at a significantly lower risk of having a child with CP. Whether further adjusting for preeclampsia, gestational hypertension, placental abruption or placental infraction, or upon using a competing risk analysis that further accounted for stillbirth and neonatal death, these results did not change. Conclusions: Immigration and ethnicity appear to attenuate the risk of CP, and this effect is not fully explained by known risk factors. © 2014 Ray et al.

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immigrant tobacco use proportional hazards model Africa south of the Sahara progeny Proportional Hazards Models Maternal Age Europe survival human risk assessment immigration Cohort Studies Middle East statistics and numerical data diabetes mellitus controlled study obesity premature labor Central America income South Asia migrant Humans male Canada Emigrants and Immigrants female chorioamnionitis maternal hypertension Pacific islands newborn large for gestational age twin pregnancy Cerebral Palsy solutio placentae population research Article delivery Retrospective Studies Ontario major clinical study mother adult small for date infant North Africa preeclampsia live birth cohort analysis stillbirth ethnicity retrospective study disease association cesarean section newborn death Child