A weight-loss intervention may be what obese mothers-to-be need to reduce pregnancy weight gain and a complicated delivery, according to a new study from the Kaiser Permanente Center for Health Research in Portland, Ore.

"Most interventions to limit weight gain among obese women during pregnancy have failed, but our study shows that with regular contact and support, these women can limit the amount of weight they gain, which will also reduce the risk of complications during and after pregnancy," Dr. Kim Vesco, lead study author and practicing obstetrician/gynecologist and clinical investigator with Kaiser, said in a press release.

The intervention was a program called Healthy Moms, and it involved half of the 114 obese women — a body mass index of 30 or more — participating in the study. These women attended a weekly support group, weekly weigh-ins, and maintained a food and exercise diary. The other half of women underwent their usual care, meeting once with a registered dietician to discuss healthy eating and exercise for pregnancy.

And after 34 weeks of pregnancy, the women in the intervention program only gained an average of 11 pounds compared to the 18 pounds women not in the program gained. Post-pregnancy, the intervention helped women lose rather than gain weight — a 6-pound loss versus 3-pound gain.

An even bigger benefit to maintaining healthy habits during pregnancy was the decreased chance of giving birth to babies large for their gestational age. Women in the intervention program were only nine percent likely to do so, whereas women receiving their usual care were 26 percent more likely to give birth to large-for-gestational age babies. The latter both complicates delivery and increases the child’s risk for obesity later in life.

"Most women in our intervention did gain some weight, but they gained and retained significantly less than women who did not participate in the intervention," Dr. Vesco said. "Even with support, it's difficult to limit weight gain during pregnancy, so women who are overweight or obese should aim for the lower end of the weight-gain range recommended by the Institute of Medicine, and they should seek support and nutritional advice to help meet their goals."

This range falls between 11 and 20 pounds. In addition to better health for both new moms and babies, limiting weight gain reduces risk for additional complications, including preeclampsia (high blood pressure and kidney damage), gestational diabtetes, and otherwise birthing injuries.