There’s little debate that exercise benefits pregnant women. But what about her fetus? And what about her labor and delivery?
Those are questions the International Olympic Committee (IOC) addresses in a new consensus statement. Not an Olympian? You might wonder why you need to pay attention to anything the IOC says, but its consensus statement covers recreational and elite athletes. In fact, the committee repeatedly notes in its statement that virtually all of the research it reviewed dealt with recreational athletes, not Olympians. That’s not surprising, considering that recreational athletes way, way, way outnumber Olympic-caliber athletes.
The good news is that, at the very least, exercise isn’t going to harm your fetus or make your labor more difficult, and in some cases it might be beneficial, according to the IOC. What follows is a summary of the committee’s conclusions after reviewing the scientific literature:
Fetal heart rate: The normal fetal heart rate is 110 to 160 beats per minute, but when pregnant women exercise, no matter the intensity, the rate increases by an average of 10 to 15 beats per minute, a sign that the fetus is getting plenty of oxygen. That’s a good thing, because whenever you exercise, whether pregnant or not, blood is directed to the muscles you’re moving. While there have been reports of the fetal heart rate slowing when pregnant women exercised intensely, such episodes were transient and not thought to mean anything.
Miscarriage risk: Intense exercise might slightly increase the increased risk for miscarriage—the loss of a pregnancy during the first 20 weeks–early on, around the time the embryo implants in the uterine wall, although the evidence is scant. Past that point in a pregnancy, the evidence that strenuous exercise can increase miscarriage risk is limited. And light-to-moderate physical activity doesn’t increase miscarriage risk and might lower it.
Preterm birth: Babies are considered to be preterm if they’re born before the end of 37 weeks’ gestation. In five recent studies, researchers compared the pregnancies of women who participated in aerobic exercise classes to women who didn’t and found no difference in preterm birth rates between the two groups.
Apgar score: Apgar scores assess how well newborns have adjusted to life outside the womb 1 and 5 minutes after birth. Scoring takes into account such characteristics as a baby’s color, heart rate, muscle tone and respiration. A score of 0-3 might be correlated with a higher risk of death. Few studies have evaluated the impact of maternal exercise on Apgar scores, but what research has been done suggests it has no effect.
Induction of labor, episiotomy and epidural anesthesia: Studies have found that exercise during pregnancy doesn’t effect a woman’s chances of any of these interventions.
Prolonged labor: The conventional wisdom has held that elite athletes might have a longer-than-average second stage of labor–during which women work to push out their babies–because of their increased muscle tone. However, research findings suggest that physical activity during pregnancy either shortens or has no effect on the duration of labor.
C-section: Obesity increases a woman’s chance of needing a c-section, which is why it intuitively makes sense that exercise during pregnancy might decrease the risk. Research findings are inconsistent, but overall, studies have found that women who exercised while pregnant had a slightly lower risk of delivering via c-section.
The bottom line is that concern about the effect of exercise on your pregnancy is not an excuse to skip your workouts. At the very least, the exercise will benefit you and, especially after the earliest days of your pregnancy, will have little effect on your baby.
Also on this topic: Exercise During Pregnancy May Improve Your Baby’s Brain.