OBJECTIVES: To investigate the association between maternal pre-pregnancy BMI and risk of cerebral palsy (CP) in offspring.
METHODS:The study population consisted of 188 788 children in the Mothers and Babies in Norway and Denmark CP study, using data from 2 population-based, prospective birth cohorts: the Norwegian Mother and Child Cohort Study and the Danish National Birth Cohort. Prepregnancy BMI was classified as underweight (BMI <18.5), lower normal weight , upper normal weight ), overweight , and obese (BMI ≥30). CP diagnoses were obtained from the national CP registries. Associations between maternal prepregnancy BMI and CP in offspring were investigated by using logbinomial regression models.
RESULTS:The 2 cohorts had 390 eligible cases of CP (2.1 per 1000 live-born children). Compared with mothers in the lower normal weight group, mothers in the upper normal group had a 40% excess risk of having a child with CP (relative risk [RR], 1.35; 95% confidence interval [CI], 1.03-1.78). Excess risk was 60% (RR, 1.56; 95% CI, 1.21-2.01) for overweight mothers and 60% (RR, 1.55; 95% CI 1.11-2.18) for obese mothers. The risk of CP increased ∼4% for each unit increase in BMI (RR, 1.04; 95% CI, 1.02-1.06). Estimates changed little with adjustment for mother's occupational status, age, and smoking habits.
CONCLUSIONS:Higher prepregnancy maternal BMI was associated with increased risk of CP in offspring.a Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway; b Department of Pediatrics, Haukeland University Hospital, Bergen, Norway; c Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, North Carolina; d Ms Forthun was responsible for the analysis and interpretation of data, and the drafting of the manuscript; Dr Wilcox participated in the analysis and interpretation of data and reviewed and revised the manuscript; Drs Lie and Moster provided advice regarding study design, participated in the interpretation of data, and reviewed and revised the manuscript; Drs Strandberg-Larsen, Nohr, and Surén participated in the interpretation of data and reviewed and revised the manuscript; Dr Tollånes proposed the study, participated in the analysis and interpretation of data, and reviewed and revised the manuscript; and all authors approved the fi nal manuscript as submitted. The prevalence of overweight and obesity among pregnant women is increasing worldwide with adverse effects on maternal and child health. 6 Obese pregnant women (BMI >29.9) have increased risk of gestational diabetes, hypertension, and preeclampsia, and their offspring are at increased risk of preterm birth, macrosomia, complications during delivery, and perinatal death. 6 -9 Maternal obesity is also associated with birth defects, in particular neural tube defects. 10 We used pooled data from 2 large prospective Nordic birth cohorts to investigate the association between BMI before pregnancy and risk of CP in offspring, both overall and for variou...