Most obese women gain more weight than is recommended during pregnancy, and may find those pounds tough to shed in the long run, a new study suggests.

In a study of 1,656 obese women who gave birth over five years, researchers found that about three-quarters gained more than 15 pounds during pregnancy - which at the time was the recommended weight gain for obese women.

Moreover, those extra pounds did not easily disappear after childbirth, according to findings published in the journal Obstetrics & Gynecology.

In general, the study found, the more pregnancy pounds a woman gained, the more she retained one year after giving birth.

Compared with women who gained less than 15 pounds, those who put on more than 15 to 25 pounds were twice as likely to remain more than 10 pounds over their pre-pregnancy weight. Those odds were increased eight-fold among women who gained more than 35 pounds during pregnancy.

“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,” lead researcher Dr. Kimberly K. Vesco, of the Kaiser Permanente Center for Health Research in Portland, Oregon, said in a written statement.

She noted that the excess weight gain is not only a problem for women’s future health, but can also boost the risk of pregnancy complications and difficult delivery. Among the possible complications are gestational diabetes and pre-eclampsia, a potentially dangerous condition marked by high blood pressure, fluid retention and protein in the urine.

Because of the risks, experts recommend that obese women gain less than what is recommended for normal-weight women during pregnancy. At the time of this study, the Institute of Medicine, an advisory body to the federal government, suggested that obese pregnant women gain about 15 pounds.

Recently, though, the IOM set an upper limit for weight gain, and now suggests that obese pregnant women put on a minimum of 11 pounds and no more than 20.

Among the women in the current study, one-quarter gained up to 15 pregnancy pounds, while 21 percent gained more than 35 pounds. Most of the other women fell somewhere in between, though about 5 percent actually lost weight during pregnancy.

On average, the study found, the women retained 40 percent of their pregnancy weight one year after giving birth. For a women who gained 15 pounds, that would mean 6 extra pounds at the one-year mark; and it would mean 12 extra pounds for a woman who gained 30 during pregnancy.

“We need to do a better job of helping obese women control weight gain during their pregnancies,” Dr. Victor Stevens, another Kaiser Permanente researcher who worked on the study, said in the statement. “Once the baby is born, it’s much harder to change eating habits and start an exercise program.”

The researchers offer some suggestions for limiting excess pregnancy pounds: eating regular meals and small healthy snacks between meals - including eight servings of fruits and vegetables, three servings of low-fat dairy and 5 ounces of protein-rich foods every day; avoiding sweets and sugary drinks; and exercising for at least 30 minutes a day on most days of the week.

They also recommend that women increase their daily calories by no more than 100 calories beyond their pre-pregnancy intake. Fat, they say, should be limited to less than 30 percent of calories, and come in the form of “good” unsaturated fats - from sources like nuts and canola and olive oils.

SOURCE: Obstetrics & Gynecology, November 2009.