(HealthDay News) – Maternal overweight and obesity, as measured by body mass index (BMI) in early pregnancy, is associated with increased risks of preterm delivery, especially extremely preterm delivery, according to a study published in the June 12 issue of the Journal of the American Medical Association.
Sven Cnattingius, MD, PhD, from the Karolinska University Hospital in Stockholm, and colleagues conducted a population-based study of 1,599,551 women with live singleton births from 1992–2010 in Sweden. The authors sought to examine the correlation between early pregnancy BMI and the risk of preterm delivery (extremely preterm, 22–27 weeks; very preterm, 28–31 weeks; and moderately preterm, 32–36 weeks).
The researchers found that as BMI increased so did the risks of extremely, very, and moderately preterm deliveries, with overweight and obesity-related risks highest for extremely preterm delivery. The rate of extremely preterm delivery was 0.17% among normal-weight women (BMI, 18.5 to <25kg/m²); 0.21 for women with a BMI of 25 to <30kg/m²; 0.27% for BMI of 30 to <35kg/m²; 0.35% for BMI of 35 to <40kg/m²; and 0.52% for BMI of ≥40kg/m² (adjusted odds ratios, 1.26, 1.58, 2.01, and 2.99, respectively). Among obese women (BMI of ≥30kg/m²), the risk of spontaneous extremely preterm delivery increased with BMI. Among overweight and obese women, the risks of medically indicated preterm deliveries increased with BMI.
“In Sweden, maternal overweight and obesity during pregnancy were associated with increased risks of preterm delivery, especially extremely preterm delivery,” the authors write. “These associations should be assessed in other populations.”