June 5, 2019

Should pregnant runners go the extra mile?

A sports medicine doctor offers guidelines to help pregnant runners continue to reap the physical and mental benefits of their sport.

Running is one of the most common sports for recreational athletes, with more than 18 million Americans registering for a running event in 2017. But are jogging and running safe during pregnancy?

We asked Susan M. Joy, MD, co-director of the Kaiser Permanente Sports Medicine Center in Sacramento, California, to provide guidance about what pregnant runners can do, what they should watch for, and if they can indeed go the extra mile.

What exercise guidelines should pregnant runners follow?

For decades, pregnant women were told to take it easy. The truth is, during an otherwise normal pregnancy, it is far more problematic for both a mother and her unborn child if she is inactive, gains unnecessary weight, and/or develops gestational diabetes than if she continues a smart training and running program.

In general, sports medicine experts say that an active runner with no pregnancy-related complications can continue to run during pregnancy, though she should not exceed the intensity of her pre-pregnancy activity. That said, it’s not necessarily the best time to push for a personal best or to start running.

Theoretically, intense exercise could divert blood flow to the working muscles and away from the placenta, which could adversely affect the developing fetus. However, many women have competed in runs late into pregnancy with no adverse outcomes, leading some to question the degree of potential danger.

It is very important for a woman to discuss her exercise habits with her ob-gyn or primary care physician at the start of the pregnancy.

What physical changes should pregnant runners expect?

Pregnant runners need to be aware of several physiological changes.

With weight gain and a growing uterus, it can feel essentially like running with a bowling ball, and thus can affect mechanics or alter the body’s center of gravity. This may affect gait and posture and could lead to injury, such as low back pain, by overloading different areas not accustomed to the changing movement patterns.

Later in pregnancy, the body experiences an increase in relaxin, a hormone that helps relax tissue and prepare the body for delivery. This has been implicated as a possible risk factor for injury during pregnancy but is not generally considered a reason to stop running. Instead, pregnant runners should pay attention to their gait patterns, stay attuned to any changes, and consult their ob-gyn if they have concerns.

Should women consider limiting their heart rate?

In the past, recommendations for pregnant women were to keep their heart rate lower than 140 beats per minute while exercising. However, there is really no data to support that restriction. If a woman is a fit runner prior to pregnancy, she can certainly start out with the same zones during an uncomplicated pregnancy.

At times, some women have to alter their training zones for comfort later in pregnancy. At more moderate levels of training, the “talk test” is a helpful one for monitoring intensity. If a woman is able to carry on a casual conversation while running, she is exercising at an appropriate level.

What about training for long distance while pregnant?

The question of whether to train for longer races while pregnant starts with one’s pre-pregnancy training. A seasoned runner experienced with that training could plan to race while pregnant.

However, the reality for most women is that the longer distance races become more difficult as the pregnancy progresses, no matter how conditioned they are.

Also, heat and hydration need to be very carefully considered for longer distance runs as the developing fetus is depending upon the mother’s temperature regulation and circulating blood volume. Similarly, altitude effects can be magnified during pregnancy, so women need to take that into consideration as well.

Generally, a woman with an uncomplicated pregnancy can continue with her pre-pregnancy running program after discussing any necessary modifications with her ob-gyn. Staying active in that case is far better for both the mother and her developing child.

Learn more about healthy pregnancy.