Association between maternal body mass index in early pregnancy and incidence of cerebral palsy

1. This retrospective cohort study found that among Swedish women with singleton children, maternal overweight and obesity were significantly associated with incidence of cerebral palsy

2. This association was limited to children who were born at full term and was partially mediated by asphyxia-related neonatal complications.

Evidence Rating Level: 2 (Good) 

Study Rundown: Cerebral palsy is the most common pediatric motor disability, leading to significant lifetime disability for children and their families, and shortened life expectancy. While few preventable risk factors are known to be associated with an increased risk of cerebral palsy, one previous, small-scale study suggested an association between maternal BMI and cerebral palsy. However, this relationship has not been confirmed in a larger-scale study. Therefore, this retrospective, population-based cohort study evaluated women with live singleton births between 1997 to 2011 to assess for any connections between maternal BMI and the risk of cerebral palsy. Its results showed a significant association between maternal obesity and cerebral palsy in children born at full term. Additionally, malformations of the nervous system, asphyxia-related neonatal morbidities, and a low Apgar score (<7) at 5 minutes were associated with the largest increases in cerebral palsy risk.

This study confirms the finding that increased maternal BMI appears to be linked with an increased risk of cerebral palsy in their newborn. The large sample size allowed for specific subgroup analyses, further shedding light on potential pathways that could mediate this effect. Some limitations include the retrospective design of this study, a small degree of missing information among mothers, and differing cerebral palsy classifications in Europe and America that may limit the generalizability of results.

Click to read the study in JAMA

Relevant Reading: Prenatal Factors in Singletons with Cerebral Palsy Born at or near Term.

In-Depth [retrospective cohort study]: This retrospective cohort study evaluated the association between maternal BMI and the incidence of cerebral palsy in their children. Patient cases were obtained from several nation-wide patient registries including the Medical Birth Register, National Patient Register, Education Register, and Cause of Death Register. Maternal BMI was calculated from self-reported height and weight measurements during initial prenatal visits. Covariates assessed in this study included maternal age, parity, cohabitation with the child’s father (a purported indicator of socioeconomic status), smoking, and length of gestation.

A total of 1,423,929 singleton births were included, among which there were 3,029 children diagnosed with cerebral palsy over a median 7.8 years of follow-up. The risk of cerebral palsy was 2.13 per 1,000 live births. Of all children with cerebral palsy, 71% were born at full term.

Rates of cerebral palsy increased with maternal overweight and obesity among children born at full term. Early pregnancy BMI was positively related to cerebral palsy rates. Compared with children of normal weight mothers, the adjusted HR of cerebral palsy for overweight was 1.22 (95%CI, 1.11-1.33) and for obesity grade 1 was 1.28 (95% CI, 1.11, 1.47), grade 2 was 1.54 (95% CI, 1.24-1.93) and grade 3 was 2.02 (95%CI, 1.46-2.79). In mediation analyses for consequences of maternal obesity that may in turn cause cerebral palsy among children born at full term, an estimated 45% of the association between BMI and cerebral palsy was mediated through asphyxia-related neonatal complications.

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