Marathon Winner Ran Throughout Her Pregnancy. Should You?

An expert on exercise and health talks about how much activity is OK for the average pregnant woman.

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A pregnant Paula Radcliffe and Lord Sebastian Coe start the sixth Nike 10k Run, October 8, 2006 London, England.

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After the New York City Marathon on Sunday, Paula Radcliffe, the fastest woman, did what a lot of parents do: She hugged her daughter. What's remarkable, though, is that little Isla was born only in January. Radcliffe trained until the day before she went into labor and started up again less than two weeks after giving birth. The American College of Obstetricians and Gynecologists recommends that after getting their OB's OK, pregnant women without medical or obstetric complications (like badly controlled high blood pressure or bleeding during the last two trimesters) should exercise moderately to achieve exercise's proven health benefits and stave off things like backaches, swelling, and even gestational diabetes. For women who don't have any complications and already run, that means you can keep going. We asked Jim Pivarnik, a kinesiologist who has studied exercise in pregnant women and is director of the Center for Physical Activity and Health at Michigan State University, how women inspired by Radcliffe can safely follow her example.

So it's fine for most pregnant women with uncomplicated pregnancies to exercise?
The caveat is that you always make sure your healthcare provider is in the loop and you don't go crazy doing more than you did before you were pregnant.

ACOG says it's OK to keep running if you're already a runner, but that you may have to modify your routine by cutting back on the miles or the intensity.
It's one thing to start up a walking program during pregnancy, and another thing to start running for the first time. But if you're having a healthy pregnancy and are already a runner, there's no reason to go from 60 miles a week to walking.

What's the potential downside of too much exercise during pregnancy?
We can get worried about low birth weight [defined as less than 5½ pounds]. A woman who is running 60 miles a week may be battling to get enough nutrition for her own needs, and if something's gotta give, it may be the baby's size. But you can get ultrasounds during pregnancy to indicate whether the baby is where it's supposed to be, sizewise.

And merely lighter-than-average babies aren't necessarily bad, right?
No. Babies born to exercisers are lighter, and being born with less fat may set you up better in adulthood for dealing with weight gain. We don't know that yet.

So how do you make sure you and your baby stay healthy if you're a runner?
You need to be vigilant about calorie intake—really careful to balance out running with eating. Some people get into trouble because they are running just to keep their figure.

What about joint problems?
The hormone changes that make your pelvis ready for childbirth aren't so selective that they don't affect other joints. And that's more of a concern for people who aren't used to running.

And what about exercise and the risk of preeclampsia?
Exercise may actually prevent it; those who were most physically active were less likely to develop preeclampsia later in pregnancy.

Can working out during pregnancy make labor and delivery easier?
There's some evidence that it makes labor a little shorter and can lead to less tearing. All the women runners and athletes I know said they wouldn't have wanted to go through labor unless they'd done weights beforehand. It's an athletic event—you are essentially weightlifting with your uterus.

Can pregnancy and childbirth actually make women perform better afterward?
I saw Paula Radcliffe on TV after the race, and she was saying that yes, she did feel stronger and better after having Isla, but that a lot of it had to do with being happy at having a baby. It can improve your mental state.