Background: Maternal overweight and obesity increase risks of pregnancy and delivery complications and neonatal mortality, but the mechanisms are unclear. The objective of the study was to investigate associations between maternal body mass index (BMI) in early pregnancy and severe asphyxia-related outcomes in infants delivered at term (≥37 weeks).
Methods and findings: A nation-wide Swedish cohort study based on data from the Medical Birth Register included all live singleton term births in Sweden between 1992 and 2010. Logistic regression analyses were used to obtain odds ratios (ORs) with 95% CIs for Apgar scores between 0 and 3 at 5 and 10 minutes, meconium aspiration syndrome, and neonatal seizures, adjusted for maternal height, maternal age, parity, mother's smoking habits, education, country of birth, and year of infant birth. Among 1,764,403 term births, 86% had data on early pregnancy BMI and Apgar scores. There were 1,380 infants who had Apgar score 0-3 at 5 minutes (absolute risk = 0.8 per 1,000) and 894 had Apgar score 0-3 at 10 minutes (absolute risk = 0.5 per 1,000). Compared with infants of mothers with normal BMI (18.5-24.9), the adjusted ORs (95% CI) for Apgar scores 0-3 at 10 minutes were as follows: BMI 25-29.9: 1.32 (1.10-1.58); BMI 30-34.9: 1.57 (1.20-2.07); BMI 35-39.9: 1.80 (1.15-2.82); and BMI ≥40: 3.41 (1.91-6.09). The ORs for Apgar scores 0-3 at 5 minutes, meconium aspiration, and neonatal seizures increased similarly with maternal BMI. A study limitation was lack of data on effects of obstetric interventions and neonatal resuscitation efforts.
Conclusion: Risks of severe asphyxia-related outcomes in term infants increase with maternal overweight and obesity. Given the high prevalence of the exposure and the severity of the outcomes studied, the results are of potential public health relevance and should be confirmed in other populations. Prevention of overweight and obesity in women of reproductive age is important to improve perinatal health.