Overweight Women Have a Greater Risk of Preterm Birth

Women who are overweight and obese during pregnancy may have an increased risk of preterm delivery, according to a study published in the June 12, 2013, edition of JAMA.

The population-based study included more than 1.5 million women who gave birth between 1992 and 2010 and were included in the Swedish Medical Birth Register. Preterm deliveries were categorized as extremely preterm (22 to 27 weeks of gestation), very preterm (28 to 31 weeks), or moderately preterm (32 to 36 weeks). Births were also defined as either spontaneous or medically indicated.

The risk of preterm deliveries was greater for overweight and obese women than for normal-weight women—particularly for extremely preterm deliveries. The rate of extremely preterm delivery among normal-weight women was 0.17%. The rate of extremely preterm delivery among overweight and obese women increased with increasing body mass index (BMI), ranging from 0.21% for women with a BMI between 25 and 30, to 0.52% for women with a BMI of 40 or higher. The risk of extremely preterm spontaneous deliveries was also increased among obese women, and the risk of all types of medically indicated preterm deliveries was increased among both overweight and obese women.

The authors conclude that the associations between obesity and preterm pregnancy should be studied in other populations.