Obese Women Gain Too Much Weight In Pregnancy, Then Retain Weight A Year Later

This is the largest U.S. study to examine the relationship between excessive weight gain during pregnancy and weight retention specifically in pregnant women who are obese. Funded by the Centers for Disease Control and Prevention, the study of 1,656 obese women found that most of them gained too much weight during pregnancy, then, on average, kept on 40 percent of the weight one year after they gave birth.

"We found that nearly three quarters of obese women gain too much weight during pregnancy -- and the more weight they gain, the harder it is to lose," said study lead author Kim Vesco, MD, MPH, a practicing OB/GYN and an investigator at the Kaiser Permanente Center for Health Research. "This extra weight also increases the risk of pregnancy and delivery complications like diabetes, preeclampsia, bigger babies, C-sections, and birthing injuries." Vesco is also leading a new study to help obese women maintain their weight during pregnancy. (See related release on the "Healthy Moms" study.)

This study defined excess weight as more than 15 pounds, which until recently was the minimum amount of weight gain recommended for obese pregnant women by the Institute of Medicine. In May of 2009, the IOM set an upper limit for weight gain in obese pregnant women, suggesting they gain between 11-20 pounds.

This study found that, on average, women retained 40 percent of the weight they gained during pregnancy one year after delivery. So if a woman gained 15 pounds during pregnancy, she could be expected to retain 6 of those pounds at one year; if she gained 30 pounds, she would retain 12 pounds.

The study included 1,656 Oregon and Washington women enrolled in the Kaiser Permanente health plan whose body mass index was 30 or higher at the start of their pregnancies, and who gave birth between January 2000 and December 2005. To be included in the study, women had to have three key weight measurements recorded in their medical records: a starting weight between six months prior to conception and 12 weeks after conception; a delivery weight within two weeks after giving birth; and a follow-up weight 8-18 months after delivery.

The study looked at pregnancy weight gain and weight retained one year after delivery. Compared to women who gained less than the recommended 15 pounds, women who gained 15-25 pounds were twice as likely to retain 10 excess pounds; women who gained more than 35 pounds were nearly eight times more likely to retain at least 10 pounds. The study also found that younger women and first-time mothers were most likely to gain too much weight.

"We need to do a better job of helping obese women control weight gain during their pregnancies. Once the baby is born, it's much harder to change eating habits and start an exercise program," said Victor Stevens, Ph.D., co-author and senior investigator at the Kaiser Permanente Center for Health Research. "If we can prevent the weight gain in the first place, moms and babies will be healthier in the long run."

Authors of the study from the Kaiser Permanente Center for Health Research in Portland, Ore., include Kimberly Vesco, MD, MPH; Joanne Rizzo, MPA; Victor J. Stevens, PhD; Nancy Perrin, PhD; Donald J. Bachman, MS; and Mark Hornbrook, PhD. Authors of the study from the Division of Reproductive Health, National Center of Chronic Disease Prevention and Health Promotion at the Centers for Disease Control and Prevention in Atlanta, Ga., include Patricia M. Dietz, DrPH, MPH; William M. Callaghan, MD,MPH; and Carol Bruce, BSN, MPH.