This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.
Doctors agree: it's a good thing to exercise during pregnancy. But a new study shows that too much of a good thing can lead to problems for both mother and baby.
Now a large Danish study suggests too much exercise can increase the risk of a dangerous condition known as pre-eclampsia.
Five percent of pregnancies are complicated by pre-eclampsia, a vascular disorder which can dangerously raise mom's blood pressure and decrease blood flow to the baby.
Researchers asked 85,000 pregnant women how much they exercised in the first trimester.
Women who averaged 40 to 60 minutes a day were 65 percent more likely to get pre-eclampsia. Those who exercised more than an hour a day were 78 percent more likely to get it.
Most doctors recommend about 30 minutes a day of moderate exercise for pregnant women. If you can't carry on a conversation while exercising, you're overdoing it. They recommend less strenuous activities like walking, yoga or swimming.
Dr. Jacque Mortiz, a general obstetricians and gynecologists at New York City's St. Luke's-Roosevelt Hospital, says, "One of the best exercises in pregnancy is swimming because there's no pressure on your joints. It's enough exercise and usually you don't get short of breath."
Good prenatal care, which regularly monitors the mother's blood pressure and the baby's heartbeat, is critical.
Pre-eclampsia is more common in "the extremes" of pregnancy: the oldest and youngest moms, and the thinnest and the heaviest moms.
Exercise helps lower the risk of gestational diabetes, improves mood, lowers the risk of gestational diabetes and reduces chronic hypertension in pregnancy. When it comes to exercise, moderation is best.