There has been surprisingly little research into the effects of vigorous activity on pregnancy and delivery. But new data focused on elite athletes suggests that intense exercise may not negatively impact pregnancy outcomes.
Female athletes seem to be able to exercise safely and intensively both before and during pregnancy without increasing their risk for birth-related complications, even if they are trekking up Mount Everest, according to two eye-opening new studies.
Together, the new research undercuts widely held beliefs about strenuous physical training and pregnancy.
As anyone who has experienced pregnancy knows, it is physically taxing. That cherished little fetus-slash-vampire requires a share of its mother’s blood, fuel and oxygen.
The mother’s body adapts to the child’s needs, adding blood vessels and volume, but the environment inside the womb remains almost otherworldly, with levels of oxygen flowing to the baby that are similar to those in the thin air near the top of Mount Everest, according to past research.
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Babies obviously can thrive in this milieu or the human species would not exist. But some doctors and other experts have raised concerns about layering vigorous exercise onto the existing physical demands of pregnancy.
Experts generally agree that moderate activity is healthy and advisable for most pregnant women. Current exercise guidelines recommend that pregnant women complete about 150 minutes per week of brisk walking or other moderate exercise, the same recommendation as for people who are not pregnant.
But some experts worry that strenuous exercise, such as intensive running, cycling or weight training, could tire or injure a pregnant woman and possibly rob her child of oxygen or nutrients.
Some also believe that strenuous, high-impact exercise before or during pregnancy will increase the size and tightness of a woman’s pelvic-floor muscles, potentially increasing the risk for tears of the perineum, the tissue that connects the vagina and the anus, and otherwise making labor and delivery more difficult.
But there has been surprisingly little research into the actual effects of vigorous activity on pregnancy and delivery.
So for one of the new studies, which was published in September in the British Journal of Sports Medicine, researchers from the University of Iceland and other Nordic institutions decided to look at birth outcomes among a group of national-team and other elite athletes, who, by definition, train intensively.
They asked 130 elite female athletes and mothers about their training in the three years before they gave birth and during their pregnancies.
Some of the athletes competed in sports that involved pounding and impact, such as running and soccer. Others engaged in lower-impact sports like swimming and equestrian events.
The researchers also asked about the exercise habits before and during pregnancy of 118 Icelandic mothers who were not athletes.
Then (with permission), they examined records in the Icelandic Medical Birth Registry about each woman’s labor and delivery.
The resulting data showed that the athletes, many of whom had trained into their second trimesters or beyond, had experienced healthy pregnancies and few delivery complications. Their labor was not more prolonged than in the control group, and they were no more likely to need an emergency cesarean section.
Statistically, they also were less likely overall to experience a serious perineal tear during delivery than the control group, especially those athletes who competed in high-impact sports.
“The lesson of these results is that elite athletes should not expect more difficulties in childbirth than other women,” says Thorgerdur Sigurdardottir, a doctoral student at the University of Iceland who led the study.
In fact, she says, the data suggest that athletes, particularly those in high-impact sports like running, “come out quite favorably” in terms of their pregnancy and delivery outcomes.
That idea is amplified, loudly, by the findings of the second new study, which details the physiological effects of climbing to Everest Base Camp while seven months pregnant.
The study, which was published in August in the Journal of Applied Physiology, arose from serendipity, says Trevor Day, a professor of physiology at Mount Royal University in Calgary, Canada, who oversaw the research.
He and other researchers arrived in Nepal in 2016 to study Everest trekkers and discovered that one of the Sherpas assisting their group was an elite runner who also was fairly far advanced in her pregnancy.
With her permission, they outfitted her with monitors to measure her activity levels during the subsequent eight-day trek.
She turned out to be breathtakingly active, averaging more than 270 minutes of exercise every day, or nearly twice the amount often recommended for a week, even as the group approached and reached the 17,600-foot altitude of Everest Base Camp, where oxygen levels are about half those at sea level.
“It was a remarkable feat!” Day says.
Much of this activity was quite vigorous, too, according to the monitors.
But she reported no pregnancy-related distress or difficulty, gained weight normally and, two months later, gave birth to a healthy baby girl.
These two studies obviously are small, tightly focused on athletes and, in the case of the Nepalese Sherpa, singular, so the results may not be meaningful for other pregnant women wondering how much they should exercise.
“It is important to assess training during pregnancy on an individual basis and talk to your health-care providers if there is anything you are concerned about,” Sigurdardottir says.
But this new research does hint that pregnancy does not need to equate to fragility.
“Physical activity before and during pregnancy is very good for the mother, the child and the process of childbirth,” Sigurdardottir says.