Exercising during pregnancy was safe for both moms and babies in a new study of heavy women in Brazil, but fitness classes and at-home exercises didn’t keep moms-to-be from gaining too much weight.

The finding is “not surprising,” according to Dr. Patrick Catalano, a maternal-fetal medicine researcher from Case Western Reserve University School of Medicine in Cleveland.

“Lots of studies have not shown any benefits relative to weight gain in pregnancy using either diet or exercise,” said Catalano, who didn’t participate in the new research.

The U.S.-based Institute of Medicine recommends that overweight women should gain between 15 and 25 pounds during pregnancy, and obese women 11 to 20 - less than the amount recommended for normal-weight women.

Being overweight or obese while pregnant, or gaining too much weight during pregnancy, increases the chance of having a large baby and needing a Cesarean section. It also ups the risk that babies will have birth defects or grow up to be obese, researchers said.

Plus, women who gain a lot of weight during pregnancy tend to keep in on afterwards, Catalano told Reuters Health.

He said that starting an exercise or diet program mid-way through pregnancy probably isn’t as useful as intervening very early in pregnancy - or better yet, before.

‘MODERATE EXERCISE IS VERY GOOD’

In the current study, researchers led by Simony Nascimento from UNICAMP Medical School in Campinas recruited 82 heavy women who were already between three and five and a half months into their pregnancies.

They split those women into two groups. Half went to weekly exercise classes and got counseled on nutrition, weight gain and home exercises or walking they could do daily. The other women received standard prenatal care advice, but no extra information on exercise.

Regardless of whether they were assigned to do group and at-home exercise, about half of the women gained more weight than recommended upper limits.

On average, obese women gained 23 to 24 pounds in both groups. Overweight women gained an average of 22 pounds when they exercised and 36 when they didn’t, but the researchers caution that those findings were based on a small group of only 14 women.

The majority of all babies were born by c-section, but there was no difference in their health at birth based on whether or not moms exercised, Nascimento and colleagues report in BJOG: An International Journal of Obstetrics and Gynecology.

Catalano said the findings don’t take away from the fact that, “moderate exercise is very good, no question about it.” But he said that the farther women get into pregnancy, the harder it is for them to stick to an exercise program. That’s why starting with exercising and diet improvement early is so important.

One of the problems is that historically, women have been given the wrong message about eating and physical activity in pregnancy, said Dr. Raul Artal, head of obstetrics, gynecology and women’s health at Saint Louis University School of Medicine.

“Pregnancy is not a state of confinement and indulgence. It’s an ideal time for behavioral modification for the benefit of both mother and the baby,” Artal, who wasn’t involved in the new research, told Reuters Health.

He considers pregnancy an opportunity to address unhealthy behaviors in patients. “In general women are more prone to adopt healthy lifestyles in pregnancy because of the concern for the unborn child.”

Nascimento’s team also pointed out that women typically have more contact with health providers when they’re pregnant.

But, Artal added, “The sad thing is that as a society we have become more sedentary and more overweight and obese. This is not confined to pregnant women.”

In an email to Reuters Health, the researchers recommended 30 minutes of moderate exercise each day for overweight and obese pregnant women, along with stretching and nutrition counseling.

SOURCE: BJOG: An International Journal of Obstetrics and Gynecology, November 2011.