Some weight loss during pregnancy may be beneficial in extremely obese women

Some weight loss during pregnancy in extremely obese women may not harm mother or baby and may lower the risk of cesarean delivery, according to a Swedish study.

The population-based cohort study conducted at the University of Linkoping examined medical records for 46,595 obese pregnant women who gave birth between 1993 and 2008: 32,991 women with class I obesity (body mass index [BMI] 30 to 34.9); 10,068 women with class II obesity (BMI 35 to 39.9); and 3,536 women with class III obesity (BMI 40 or higher). Women with low (0 kg to 4.9 kg) or no gestational weight gain were compared with women who gained the 5 kg to 9 kg recommended by the Institute of Medicine.

Women in the class III obesity group who lost weight showed no significant increase in risk for preeclampsia, excessive postpartum bleeding, instrument delivery, low Apgar score, or fetal distress compared with those who gained the recommended amount. They also were less likely to undergo cesarean delivery (odds ratio, 0.77) or deliver a large-for-gestational age infant (odds ratio, 0.64). Findings were published in Obstetrics & Gynecology (2011;117[5]:1065-1070).

The findings suggest that some weight loss in very obese women may be “reasonably safe,” says study author Marie Blomberg, MD, PhD, but just how much is safe is unknown.

Women in obesity class III who lost weight had an increased risk of giving birth to small-for-gestational-age babies (3.7%; odds ratio, 2.34), slightly higher than the overall prevalence of such births in Sweden (3.6%). However, Class III women with low weight gain did not have a significantly increased risk of small-for-gestational-age babies.

Blomberg warns pregnant women against embarking on any weight-loss diet and urges obese women who are pregnant to consult a physician about needed changes in diet and lifestyle.