Running while pregnant is good for baby's heart: Study

I gained 60 pounds during my first pregnancy. Some of the weight gain can be attributed to emotional binge eating (I really hated being pregnant and, what can I say, donuts made me happy), but most of it came from lack of exercise. When I had unexplained bleeding during my first trimester, my doctor suggested I stop running and switch to yoga and swimming. Both of which I did, but not nearly enough to offset my daily donut habit.

I vowed my next pregnancy would be different, so when I found out I was pregnant with Gillian, the first thing I did (after getting the all-clear from my doctor), was buy a maternity running skirt and register for a half marathon. I continued running until I was 30 weeks and I'm proud to have completed four half marathons during my pregnancy.

The benefits of running and exercise during pregnancy have long been studied: Mothers who exercise have better overall mental health and it helps reduce the risk of gestational diabetes. Inspirational mothers like Olympic track athlete Alysia Montano and marathoners Kara Goucher and Paula Radcliffe have busted the myth that running during a healthy pregnancy is selfish and unsafe. But, if you needed another reason to lace up, emerging research from the Washington University School of Medicine recently published in the April 2015 issue of Nature suggests that running during pregnancy may guard against serious fetal heart defects in infants.

"Hearts develop so soon after conception that the damage is done before we even know it’s started,” says leader researcher Dr. Patrick Y. Jay. While scientists recognize that older mothers are at a greater risk than younger mothers of having babies with congenital heart disease (affecting approximately one in every 100 babies in the US), it's never been fully understood whether it's the age of the woman or her eggs that that increases the odds.

Using female mice genetically bred to have a high risk of having babies with heart defects, scientists transplanted young ovaries (containing young eggs) into the older mice and old ovaries into the younger mice. They determined the age of the ovaries and eggs ultimately played no role in the mother's risk of delivering offspring with heart defects. Suspecting activity levelsmay be a factor, scientists allowed half the mice (both older and younger) to run at will several weeks before coming pregnant (while the other half stayed sedentary). When the mice had their babies, the older mice that could run had babies with far few fewer heart defects than the sedentary mice. More than 20 percent of the sedentary mice had babies with heart defects.

Research will continue to help us understand why there were fewer heart defects in the babies born to active mice, but Jay suggests that there may be benefits to baby's heart because exercise changes the workings of some genes—which in turn releases substances from a mother's muscles and cells that end up in her womb and the fetus. This research is the first of its kind and requires more digging, but with more women becoming mothers later in life, the idea that exercise can help reduce heart defects is promising.

Follow along as Jennifer Pinarski shares her experiences about giving up her big city job and lifestyle to live in rural Ontario with her husband, while staying home to raise their two young children.

Follow her @JenPinarski.