Is Intense Exercise Associated With Very Early Miscarriages?

According to research conducted by the University of Massachusetts Amherst, women with a history of miscarriage who engaged in higher levels of physical activity had a higher risk of subclinical or very early pregnancy loss. In women with confirmed pregnancies, there was no association between physical activity and the risk of miscarriage.

Physical Activity and the Risk of Subclinical or Very Early Miscarriages

“The risk associated with physical activity is different for pregnancy losses shortly before implantation than for later, clinical pregnancy losses,” writes lead author Lindsey Russo, a doctoral student and collaborator of senior author Brian Whitcomb, associate professor of epidemiology at the School of Public Health and Health Sciences. The study provides insights into the issue of physical activity in very early pregnancy.

“The implantation phase can be a time of vulnerability when strenuous physical activity may pose a risk for subclinical or very early miscarriages,” Russo adds, although the researchers say larger studies are needed to further investigate this issue. The risk of very early miscarriage was about twice as high in women who were very active as in women who were less active. Subclinical miscarriages can be difficult to detect because they can occur before a woman even knows she is pregnant. The researchers were able to fill an interesting gap in the literature, which had conflicting evidence on whether physical activity has a negative, positive, or no effect on pregnancy. Identifying these very early pregnancy losses requires laboratory tests and daily sampling to identify pregnancies and miscarriages. Few studies are able to do this.

Don’t Overdo Physical Activity

The researchers analyzed data from the Effects of Aspirin in Gestation and Reproduction (EAGeR) study. Whitcomb, who was working at the National Institutes of Health at the time, was involved in the original four-year study, which recruited women aged 18 to 40 with one or two miscarriages who wanted to become pregnant between 2007 and 2011. The study participants used home pregnancy tests, which were combined with information from laboratory tests to confirm pregnancy through an increase in the hormone hCG, one of the earliest indicators of pregnancy. Of the 785 women who became pregnant, 188 (23.9%) suffered a miscarriage, including 55 subclinical miscarriages that were only detected by hCG tests in biosamples. Physical activity is a complicated measure, according to the researchers. It is a combination of health consciousness and the physiological effects of physical activity, which is generally good for physical health but can also cause stress.

Physical activity was defined based on time spent and intensity to calculate an overall physical activity score. The researchers are trying to provide good, evidence-based information for pregnant women who want to know what to do, as well as for doctors who advise their patients.

Russo points out that according to recommendations from the American College of Obstetricians and Gynecologists, “women with uncomplicated pregnancies should be encouraged to engage in aerobic and strength training exercises before, during, and after pregnancy.” The researchers say their study suggests that women who have lost a pregnancy should avoid strenuous activity in the earliest stages of a subsequent pregnancy or around the time of trying to conceive. “For women who are having difficulty conceiving, our findings are consistent with previous work that has also shown that high levels of physical stress during the implantation phase may be associated with an increased risk of miscarriage,” Whitcomb said.