The Benefits of Prenatal Exercise

Prenatal exercise tied to lower risk of high birth weight and fewer C-sections

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Pregnancy calls for kicking those swollen feet up and simply trying to relax, right? Maybe not. Moms-to-be might not need to be so fast to slow down.

A new study found that pregnant women who exercised were less likely to have a baby with high birth weight than those who didn't exercise.

"The issue related to improved outcomes with prenatal exercise really is not unique to pregnancy," explained Andre F. Hall, MD, a board-certified OB-GYN at Birth and Women's Care in Fayetteville, NC, in an interview with dailyRx News. "Exercise improves the functioning of most of the body's systems and simply this is carried over to pregnancy and thereby results in an improved outcome."

But according to the authors of this new review, led by Margie H. Davenport, PhD, of the Program for Pregnancy and Postpartum Health at the University of Alberta in Canada, only around 15 percent of women around the world meet pregnancy exercise guidelines. Some women may be concerned that exercise can have a negative impact on the growth of their baby.

These researchers aimed to explore the link between birth weight and exercise. In this review, a large newborn was defined as a baby whose weight was higher than the 90th percentile, or more than 4,000 grams (8.82 pounds).

Dr. Davenport and team reviewed data from 28 past studies involving 5,322 pregnant women. These studies all involved supervised exercise — this meant at least one exercise session with study personnel every two weeks during this study.

Although the frequency and type of workout varied across the studies, Dr. Davenport and team found that prenatal exercise may reduce the risk of having a large newborn by 31 percent overall. And prenatal exercise did not appear to affect the risk of having a small newborn — defined as less than the 10th percentile, or weighing under 2,500 grams (5.51 pounds).

Furthermore, moms-to-be who exercised while pregnant gained an average of 1.1 kilograms (2.43 pounds) less during their pregnancy than those who did not exercise. Women who exercised were also 20 percent less likely to deliver via cesarean section.

These women were participating in structured and supervised exercise programs. Women should discuss prenatal exercise with their doctors. However, for many women, most experts say moderate exercise is safe and healthy.

"Like most things, moderation is important when it comes to exercise in pregnancy," Dr. Hall said.

Light cardio, but not weightlifting, is usually recommended, Dr. Hall said.

"The issue with weights has nothing to do with the stress on the body but rather the concern that due to the changing body, things such as balance are altered and the risk of injury due to this change is increased," Dr. Hall said.

Dr. Hall added, "The take-home message is that people should participate in some form of exercise that increases the heart rate to 65 percent of maximum for at least 30 minutes, three to four times a week. This does not change in pregnancy unless there are specific concerns about the pregnancy that need to be discussed with a patient's individual physician."

The Mayo Clinic stressed the importance of pregnant women starting small, watching for unusual symptoms and talking with their doctors before starting an exercise program. Some conditions or situations might call for more rest.

This study was published in the May 2015 issue of the journal Obstetrics & Gynecology.

The University of Alberta Human Performance Scholarship Fund funded this research. Dr. Davenport and team disclosed no conflicts of interest.

Review Date: 
May 13, 2015
Last Updated:
May 19, 2015