June 5, 2008 -- The nation's obesity epidemic is forcing experts to rethink weight guidelines for pregnant women.
Nearly one in 10 women of childbearing age is obese, and far more than that are overweight.
The number has the Institute of Medicine (IOM) working to redraw recommendations guiding women and their doctors on weight gain during pregnancy and how to avoid becoming obese after birth.
"It's a very high proportion of women and it's a concern to us," says Kathleen Rasmussen, the head of an IOM panel to "re-examine" the pregnancy weight guidelines. "The population is quite a bit heavier than it was in the late '80s."
That's the last time an IOM panel met to make recommendations on weight during pregnancy. Experts then were concerned mostly with the effect maternal weight gain can have on infants and babies. One concern is that overweight mothers have children who are at risk of being overweight.
But researchers are now concerned with the health effects of overweight and obesity on mothers, both during and after their pregnancies.
"Now the number of women who'll enter pregnancy [being] obese has increased. So what should we tell these women?" asks Andrea Sharma, PhD, a researcher with the CDC's nutrition, physical activity, and obesity division.
Typically women gradually lose weight over the course of a year or two following a pregnancy, according to studies presented at a panel meeting Thursday in Washington, D.C. But Erica P. Gunderson, PhD, a researcher at Kaiser Permanente who studies weight gain in pregnancy, says overweight or obese women stay heavier longer after their children are born.
Gunderson presented findings from a 2004 study of about 2,000 pregnant women.
"If you start out normal weight, it was about 1 kilogram," Gunderson says, referring to women's average weight gain more than two years after delivering their first child. One kilogram is 2.2 pounds. But women who start out overweight or obese on average stayed 3 to 6 kilograms (6.6 to 13.2 pounds) heavier than their pre-pregnancy weight, she says.
"The higher you start off, the more likely you are to retain," Gunderson tells WebMD.
Most women who begin pregnancy at a normal weight run about a 10% risk of becoming overweight after they've had a child, according to Gunderson.
Rasmussen said the IOM is also looking at ways to help pregnant women control their weight. Diet and exercise are familiar recommendations, but there is also emerging evidence that adequate sleep could play a role in keeping weight down.
But experts are also mulling ways to make sure their recommendations reach the women they're intended to help.
Patricia Dietz, a researcher with CDC's division of reproductive health, said about three-quarters of women in one survey said they got weight gain advice from their health care provider during pregnancy.
"Unfortunately, we didn't have information on what they were told," she says.
Rasmussen says the IOM panel is expected to release its final report in the spring or summer of 2009.
(How much weight did your doctor advise you to gain during your pregnancy? Join others on WebMD's Pregnancy: 1st Trimester, Pregnancy: 2nd Trimester, and Pregnancy: 3rd Trimester boards to talk about it.)