Running for Two

Sound advice from doctors, researchers and runners on running during pregnancy

October 1, 2002

Before ACOG granted even hesitant blessing to pregnant runners, Debbie Grant, 37, of North Brunswick, NJ, discovered that neighbors sometimes had a hard time with the idea. Grant, a top middle-distance runner through the late 1990’s, was pregnant with her son Kyle 11 years ago, when running pregnant was much less common. "I continued to go to the track and jog," she recalls. "I was in a neighborhood with a lot of joggers. Near the end [of the pregnancy] they would see my stomach and [that] I was jogging. They would stand in front of me and say ‘Stop!’ I did slow down. This was from older women who had kids." Grant’s second son, Miles, is four; she also ran while pregnant with him.

In 1994, ACOG retracted target heart rates from their recommendations, saying that perceived exertion is a better guide to appropriate workout length and intensity. In 2000, the American College of Sports Medicine issued a reassuring statement: "...(P)articipation in regular weight-bearing exercise has been shown to improve maternal fitness, restrict weight gain without compromising fetal growth, and hasten postpartum recovery. In addition, the psychological benefits of exercise are undeniable, and should be nurtured by all who care for pregnant women." The most recent ACOG guidelines, published in January 2002, are less enthusiastic but still support exercise: "Recreational and competitive athletes with uncomplicated pregnancies can stay active during pregnancy while modifying their usual exercise routines as medically indicated."

What’s Happening?

Understanding what may or may not be medically indicated can be a challenge, since changes that happen to a pregnant runner are intense and on-going, and they start the moment a fertilized egg nestles into the uterine wall.

As soon as the egg implants, hormones flood the body, instructing the blood vessels to expand and relax. As a result, less blood moves into and out of the heart. The heart and adrenal glands respond by sending a different batch of hormones to the kidneys, instructing them not to take as much salt and water out of the blood as usual and thus helping to restore blood volume. This back-and-forth process will continue throughout pregnancy, until the mother’s blood volume will have increased nearly fifty percent.