THURSDAY, Feb. 28, 2002 (HealthDayNews) -- Having a baby? You might want to consider spending a few less hours at the gym and a little more time with your feet up, reading a good book.
That's the controversial conclusion suggested by a new study published today in the Journal of the American College of Obstetricians and Gynecologists.
A group of American and Australian researchers reports that working women who participated in heavy exercise during pregnancy experienced some decided disadvantages over those who didn't exercise at all -- including longer labors, smaller babies, and more colds and flu.
But before you trade in those running shoes for the fuzzy bunny-topped slippers, you might want to consider what one expert says: The results go against common knowledge and common sense, and they're not to be taken to heart just yet.
"I'd take this study with a giant grain of salt until a lot more research duplicates the finding," says Dr. Steve Goldstein, professor of obstetrics and gynecology at New York University School of Medicine.
Exercise, says Goldstein, has far too many positive effects, "on weight, on cardiovascular health, on mood, on bone health, to stop doing it based on this one study."
The study found that the more a working woman exercised during her pregnancy, the more problems she encountered.
"The women who did more exercise were more likely to need an induction of labor or augmentation of labor with oxytocin [a drug used to encourage labor], and had longer first stage labors, resulting in longer total labors," say the study authors.
The heavy exercisers also had slightly smaller babies. But Goldstein points out the data doesn't indicate whether they were low birth weight babies, which traditionally have some serious health problems.
"The babies were all well within normal birth weights, and nothing to be concerned about," says Goldstein.
As for the increased colds and flu seen in the most active women, the study authors hypothesize that since reduced immunity has been seen in athletes who exercise strenuously, "this may explain the observation."
The study, conducted between 1995 and 1998, involved 750 women considered to have low risk pregnancies. All were on active duty in the United States Navy, in non-combat jobs involving nursing, law, religion, clerical duties, financing and administration.
The women were categorized into one of four groups, determined by their level of exercise.
Group one had 217 women, who did no exercise.
Group two had 222 women, who did light exercise defined as aerobics that stopped in the 20th week of pregnancy. Or they did 30 minutes of Navy-mandated physical training three times a week, and stopped at 28 weeks of their pregnancy, or they exercised five times a week, and stopped at 20 weeks.
The third group had 73 women, who performed aerobic activities, stopping in the 20th week of their pregnancy, or 30 minutes of Navy-mandated exercise five times a week for 28 weeks of pregnancy.
The fourth group of 238 women were the heavy exercisers. They did mandatory Navy workouts for 30 minutes three times a week, stopping after 28 weeks, along with voluntary extra exercise that continued after 28 weeks, or mandatory Navy workouts throughout the entire pregnancy.
The women were evaluated and found to be of equal status in the number of children, maternal illness, education, income, marital status, race, height, pre-pregnancy weight, smoking rates, stress and social support, among other factors.
The only differences were seen in group four, where the women were older, exercised more at the time of their conception, and worked full time for more weeks during their pregnancy.
The study result: Thirty-three of the women in group four needed labor induction, compared to just 17 women in group 1. Likewise, group four averaged 9.8 hours for first-stage labor, while group one needed 8.3 hours.
On average, babies born to mothers in group four weighed some 86 grams less at birth than those born to mothers in group one.
Of the women in group four, 115 had colds and the flu during the study, compared to 79 women in group one.
Among the only pluses for the women who exercised: They had fewer umbilical cord abnormalities, nine, compared to 18 in group one.
Even in light of the statistical review, Goldstein remains unconvinced of the study's findings.
"Whenever you have a study that dramatically goes against conventional wisdom, as this study does, you have to keep it in perspective and recognize that it could be a fluke finding -- and not consider it a valid finding until it is duplicated in more than one additional study," Goldstein says.
He sees no reason why a pregnant woman can't exercise as much as she wants, as long as she's got her doctor's approval.
What to Do: To learn more about exercise and pregnancy, visit The American Academy of Family Physicians. To find guidelines for exercising during pregnancy, visit LifeMatters. For more information on labor and delivery, visit The National Library of Medicine.
