Be Active During Pregnancy | Health Blog

Active Mothers-to-Be Benefit Babies’ Hearts

Be Active During Pregnancy | Health Blog

It’s a very old fashioned idea that women need to be sedentary during pregnancy for the health of their unborn children. We now know that many forms of activity are safe and recommended throughout most typical pregnancies. Getting regular exercise can help mom keep her weight gain in check, her energy level high, and even make labor and delivery a little easier. And now it seems there are other possible advantages as well. According to new research, maintaining physical activity may help decrease the risk of having a baby born with a heart defect.

The study, which was conducted at Washington University School of Medicine in St. Louis, Missouri, found that, in mice at least, getting exercise during pregnancy lowered a mother’s chances of delivering offspring with congenital heart problems.1 Reynolds, Gretchen. “Mothers’ Exercise May Lower Heart Risks in Newborns.” New York Times. 8 April 2015. Accessed 12 April 2015. Rather than using human participants, the subjects were laboratory mice. They were bred to be genetically predisposed to be more likely to give birth to pups with holes between the chambers of the heart, which is a relatively common birth defect in children.

Initially, the focus of the experiment was on how the age of the mother and her ovaries might influence the formation of heart defects in offspring. So the scientists gathered a population made up of half young female mice and implanted the ovaries and eggs of much older mice in them. The other half was made up of older female mice approaching the mouse equivalent of menopause, and likewise they were implanted with the ovaries and eggs of young mice. Then all of the mice were impregnated.

The older mice had a considerably higher risk of delivering pups with heart defects, and this surprisingly held true even when they were conceived in a youthful egg within a young ovary. This led the researchers to move on to the second portion of the study, which aimed to determine what it is about older mice that results in a greater prevalence of heart problems in their offspring. They attempted to isolate factors that influence metabolism to pinpoint whether that might somehow affect the development of the fetal heart.

The first try in this arena involved feeding some of the pregnant older mice high-fat kibble while others consumed regular kibble. But all of the older mice delivered pups with heart defects at the same rate, regardless of what they were fed. So the scientists moved on to explore the impact of exercise in pregnant mice, and this was where they found a substantial difference.

Another group of female mice, both young and old and prone to having pups with heart defects, was gathered. But this time, running wheels were placed in each of their cages, and the mice were permitted to use them as much or as little as they wanted for a few weeks prior to pregnancy. A second grouping of mice with the same characteristics were not provided with running wheels in order to keep their activity levels to a minimum.

After the offspring were born, the results showed that the older mice who had exercised had less than half the chance of delivering pups with heart defects than did their similarly aged peers who were sedentary. Approximately 10 percent of the older mice that ran gave birth to pups with heart problems, while more than 20 percent of the older mice that did not exercise had pups with heart problems. Physical activity was the only factor studied that brought the heart defect levels of the pups born to older mothers down to the same rates as those seen in the younger mice who, whether they exercised or not, had a 10 percent rate of sick pups.

Obviously, we have to consider the fact that these subjects were mice and the outcomes might be very different in humans. However, we do know that getting in shape prior to conception is healthy and beneficial to both mom and baby and helps lower the chance of gaining too much weight. Performing light daily exercise such as walking is restricted in very few pregnancies. Since the fetal heart begins developing within the first weeks of the first trimester, a mother’s overall health just before and in the early stages of pregnancy may matter greatly in this essential area. So it certainly wouldn’t hurt women of any age to adopt a more nutritious diet and start working out when they are ready to start thinking of having a baby–and throughout the pregnancy, as conditions allow.


1 Reynolds, Gretchen. “Mothers’ Exercise May Lower Heart Risks in Newborns.” New York Times. 8 April 2015. Accessed 12 April 2015.

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