Maternal Prepregnancy BMI and Risk of Cerebral Palsy in Offspring

Abstract

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 (BMI 18.5-22.9), upper normal weight (BMI 23.0-24.9), overweight (BMI 25.0-29.9), 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 log-binomial 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.

FIGURE 1

Selection of study sample.

FIGURE 2

Prevalence of CP per 1000 children by deciles of BMI and cohort (the solid black line is the linear prediction in the pooled cohort).

FIGURE 3

Adjusted RR of CP subtypes by maternal prepregnancy BMI. ^aAdjusted for maternal occupational status, smoking in the first part of pregnancy, and age. Total study sample in adjusted analysis for unilateral CP: n = 185 746, 147 cases; total study sample in adjusted analysis for bilateral CP: n = 185 785, 186 cases; total study sample in adjusted analysis for dyskinetic CP: n = 185 632, 33 cases; and total study sample in adjusted analysis for ataxic CP: n = 185 611; 12 cases.