Prepregnancy maternal overweight increases the risk of both early and late preterm delivery.

Preterm delivery is defined by the World Health Organization as delivery before 37 completed weeks of gestation. It is of great importance because it is a leading cause of neonatal death and morbidity. Preterm delivery is responsible for 3 million deaths worldwide annually.

Maternal obesity is a growing public health problem worldwide. It is known that women with excess weight have a higher risk of several adverse maternal and perinatal outcomes that include preeclampsia, gestational diabetes mellitus, cesarean section delivery, and fetal death. Women with lower than normal body mass index also have an elevated risk of adverse prenatal outcomes, such as preterm delivery and intrauterine growth restriction.

The findings in this study support the hypothesis that high pre-pregnancy maternal body mass index increases the risk of preterm delivery says Dr. Morken, one of the authors of the study. According to Dr. Morken the results showed that pre-pregnancy maternal overweight was associated with increased risk of both early and late preterm delivery. The increased risk of preterm delivery was strongest in the highest obesity group. Women with pre-pregnancy obesity had increased risk of spontaneous preterm delivery, but not medically indicated (iatrogenic) preterm delivery.

Dr. Morken says the study indicates that pre-pregnancy body mass index is an important determinant of preterm delivery risk, independent of sociodemographic, health, and lifestyle variables. Therefore, weight reduction before pregnancy could help overweight women to reduce the risk of preterm delivery.

Link to full-text article: http://www.sciencedirect.com/science/article/pii/S0002937812005947