Should pregnant women run marathons?

By Deborah Kotz, Globe Staff

I ran regularly through the first six months of my pregnancies and completed a marathon when I wasn’t pregnant, but I would never have thought to actually train and compete in a marathon while pregnant. Thus, I was amazed to hear about Amber Miller, the woman making headlines this week for going into labor just minutes after finishing the Chicago Marathon on Sunday.

She was nearly full-term and thankfully her baby was born healthy. Still, I can’t help but think, is this woman crazy?

Miller says her doctor gave her clearance to run half the marathon. She decided to run half and walk the rest.

“Good for her,” said Dr. Laura Riley, medical director of labor and delivery at Massachusetts General Hospital. She assured me that Miller’s marathon participation wasn’t crazy, considering that she started her pregnancy in good physical condition.

In May, the 27-year-old ran the Wisconsin Marathon in 4:23 while 17 weeks pregnant with her daughter, according to the Associated Press. In 2009, she ran the Indianapolis Marathon in 4:30 while she was 18 weeks pregnant with her son who’s now a year old. She finished the marathon on Sunday in 6:25 due to her decision to walk the last half.

While pregnant women were once told to monitor their heart rates carefully and avoid strenuous activity, they’re now encouraged to remain just as active -- and even start exercising if they were sedentary before pregnancy. And, no, they don’t need to take their pulse or avoid running, said Riley. “I tell my patients they can work out hard, as long as they can talk through it. They shouldn’t exercise to the point of exhaustion.”

The American College of Obstetricians and Gynecologists recommends that pregnant women engage in some physical activity for at least 30 minutes on most days of the week to help prevent pregnancy woes like backaches, constipation, bloating, and swelling.

Exercise can also improve a woman’s mood, sleep patterns, and ability to cope with labor. The muscle tone, strength, and endurance it provides can also make it easier to get back in shape after the baby is born.

Pregnant women should, though, avoid scuba diving since it could deprive the baby of oxygen, as well as contact sports and skiing, which pose high risks for injuries. “They also need to recognize that they have high levels of the hormone relaxin, which makes their ligaments and joints looser,” said Riley, making it easier for the body to accommodate a growing baby but also to pull a muscle during sudden movements.

While women at higher risk of preterm labor may be told to avoid exercise, nearly everyone else can continue their normal level of activity, with their doctor’s consent, for as long as they feel comfortable, said Riley.

“Women tend to modify it as they get larger and tire more quickly,” Riley said, “but under-exercise is usually far more of a problem than over-exercise. Women come to labor and delivery and don’t have the strength to push a baby out.”

Obstetricians are seeing more and more obese pregnant women, and experts believe this had led to a rise in caesarean sections, hypertension, and gestational diabetes, all of which occur more frequently in overweight women. Babies born to obese mothers also fare worse, having a higher risk of certain birth defects and health problems later on, such as asthma and obesity.

Regular exercise can help women gain less excess weight when pregnant to help them avoid C-sections and pre-term births, which are also more common among obese women.

Swimming, walking, and exercise classes designed for pregnant women may be best for those who were couch potatoes before getting pregnant. (Here’s our list of Boston-area pregnancy and new mom fitness classes.)

Staying well-hydrated during workouts by toting a bottle of water is key, said Riley, since pregnant women face a higher risk of dehydration. Also, they should be aware of warning signs that indicate they should stop exercising immediately and call their doctors. These include vaginal bleeding, dizziness, chest pain, calf pain or swelling, and uterine contractions. Decreased fetal movement can also be a sign that something is wrong.