Experts say that the chances of delivering an overweight baby (more than 8 pounds—4000 grams) are likely to reduce by 28 percent for expecting mothers who exercise at least three times per week in their second and third trimesters of pregnancy.

"Women often adopt healthier habits before and during pregnancy, like stopping caffeine use. This study suggests that adding exercise to that list may be icing on the cake," said Dr. Robert Welch, chairman of obstetrics and gynecology at Providence Hospital in Southfield, Michigan.

Regular exercise: a key to keeping the baby size normal
In order to measure the effect of exercise on the newborn’s weight, the Norwegian researchers analyzed data from the Norwegian Mother and Child Cohort study which included information on nearly 37,000 women.

All these women were pregnant with one child, 2/3 of the women had normal weight, while 20 percent of women were overweight but not obese. Information on the exercising regime of these women was collected at weeks 17 and 30 of their pregnancies.

An analysis of the exercising statistics revealed an association between regular exercise -- at least three times a week -- and reduced risk of having an overweight baby.

The risk for overweight newborns fell by 28 percent for first time moms who were exercising during the 17th week of their pregnancy and 23 percent for those who were exercising at week 30.

The findings of the study also suggested that 11 percent of newborns were classified as being in the 90th percentile or more of birth weight, labeling them as "excessive".

The study further suggested that pre-pregnancy exercise didn’t have any effect on the baby’s size, but exercise during pregnancy did.

Effects of exercise appeared inconsistent in second time mothers
Approximately, 43 percent of the first time mothers reported that they exercised three times a week or more before pregnancy. And 32 percent of pregnant women who already had children also reported that they exercised three times a week or more.

For women who’d already had children, the effects of exercise did not appear to be very beneficial and the reason for the same has yet not been established. However, the likelihood of delivering a large baby was reduced in such women when they danced or participated in low-impact aerobics. But the benefits did not show when they swam or trained in fitness centers.

Being unable to address the issue in this study, the researchers are considering the present findings as the basis for further study.

Overweight baby causes problems
Experts say that excessive newborn weight can have severe consequences on mother’s and newborn’s health. It can also pose an increased risk of obesity both for the mother and the child later in life.

If a baby weighs more than 8.8 pounds, it increases the risk of delivery problems, C-sections-- cesarean surgeries, postpartum hemorrhage-- severe bleeding after birth, and requires low Apgar test-- test designed to quickly evaluate a newborn's physical condition after delivery and to determine any immediate need for extra medical or emergency care.

Workout is also associated with lowering glucose levels in both disease-free women and those who have gestational diabetes, as shown by research.

Therefore, moderate physical activity is highly recommended by doctors during pregnancy.

Precautions to be taken while exercising during pregnancy
Women should take all possible precautions while exercising during pregnancy, say experts.

They should avoid any exercises which puts them flat on their back because this prevents the blood flow to the baby and the mother.

Any sport like horseback riding which involves a risk of falling off or causing a blunt force to the abdomen should be avoided.

The heart rate should also be monitored during pregnancy. It should not go below 120 beats per minute as this level keeps the blood flow to the baby adequate.

The study is published in the journal Obstetrics & Gynecology.