Heavy Strength Training During Pregnancy: What the Latest Research Says

For years, exercise has been encouraged during pregnancy because of its many benefits for both mother and baby. Strength training, in particular, has been shown to help maintain muscle, support functional movement, and improve overall health throughout pregnancy.

However, one recommendation has remained relatively consistent: avoid lifting heavy weights. While lower- to moderate-intensity strength training has long been considered safe, heavier resistance training has often been discouraged out of concern for maternal and fetal health.

A new study published this month in the British Medical Journal provides the strongest evidence to date that this concern may be overstated.

Researchers conducted the largest study ever examining the immediate effects of heavy-load resistance training on fetal heart rate and uteroplacental blood flow. Their findings suggest that heavy strength training—including exercises performed in a supine (lying on the back) position—does not negatively affect fetal well-being in healthy, physically active pregnant women.

The authors concluded:

"This is the largest study to date on the acute effects of heavy-load resistance training on fetal heart rate and uteroplacental blood flow. The results suggest that engaging in heavy-load resistance training, including supine exercise, does not pose a risk to fetal well-being in healthy, active pregnant women. These results will help athletes, coaches and healthcare professionals develop safe and effective training strategies during pregnancy. The results will inform the development of evidence-based guidelines for the inclusion of heavy-load resistance training in prenatal exercise programs."

These findings are significant because they challenge long-held assumptions about what is—and isn't—appropriate during pregnancy. Rather than avoiding heavier resistance training altogether, healthy, active women may be able to continue lifting heavy weights safely under appropriate supervision and with guidance from their healthcare provider.

As always, exercise recommendations should be individualized. Every pregnancy is different, and women with medical conditions or pregnancy-related complications should follow the advice of their physician or obstetric care provider.

The Take-Home Message

The latest evidence suggests that heavy strength training is both safe and effective during pregnancy for healthy, active women. This includes lifting heavier loads and performing exercises in a supine position—activities that have traditionally been discouraged despite limited evidence supporting those restrictions.

As research continues to evolve, one thing remains clear: strength training is an important component of a healthy pregnancy, and the evidence supporting its safety continues to grow.