Strength training during pregnancy may help lower the risk of gestational diabetes, but a new study suggests the evidence is promising rather than conclusive.
In a randomized clinical trial of 209 pregnant women with overweight or obesity, gestational diabetes developed in 2% of those assigned to a strength-training program compared with 7.3% of those receiving standard prenatal care. The difference did not reach statistical significance, which means researchers could not be certain the lower rate was caused by the exercise program rather than chance.
The study, published in Acta Obstetricia et Gynecologica Scandinavica, also found clearer benefits in how women felt during pregnancy. Those in the strength-training group reported better quality of life and fewer pregnancy symptoms that interfered with daily activities.
Participants entered the study during their first trimester and all had a BMI of at least 25. Women with pre-existing diabetes, chronic high blood pressure, cardiovascular disease or a history of preterm delivery were not included.
Starting around weeks 12 to 14 of pregnancy, women in the exercise group were offered one supervised strength-training session a week and encouraged to complete two additional sessions at home. The program continued through week 36 or delivery.
The workouts used resistance bands or light weights and targeted major muscle groups, including the back, shoulders, arms, abdomen and glutes. Both groups received standard prenatal care and written dietary guidance for pregnancy in women with overweight or obesity. The control group was still free to exercise on its own.
By the time participants were screened for gestational diabetes, two women in the strength-training group had developed it compared with seven in the control group.
That gap caught the researchers' attention, but the study was relatively small and there were only a few cases of gestational diabetes overall. Because of that, the trial could not show with confidence that strength training prevented the condition.
The result looked even more striking among women who stuck more closely to the exercise plan.
Among the 75 women with adherence information, 36 completed at least two strength-training sessions a week. None of those women developed gestational diabetes, compared with 7.3% of women in the control group.
But that finding needs extra caution. Women were randomly assigned to the exercise program, but they were not randomly assigned to follow it consistently. Women who kept up with the workouts may have differed in other ways from those who did not, so researchers cannot say that adherence itself prevented gestational diabetes.
“Our findings suggest that adherence to a structured strength training program during pregnancy may help reduce the risk of gestational diabetes while also improving maternal well-being,” said corresponding author Teresa E. Santa Cruz, MD, of Hospital Universitario Donostia in San Sebastián, Spain. “Further research is needed to confirm these findings and to determine how strength training can best be incorporated into routine prenatal care.”
The strongest results were not about diabetes.
Women assigned to strength training had better quality-of-life scores by late pregnancy and reported fewer symptoms affecting their daily lives. These included fatigue, anxiety, digestive problems, lower back pain, pelvic pain and sciatica.
They also became more physically active overall.
The study did not find meaningful differences between the groups in gestational weight gain, average newborn weight, high blood pressure or preeclampsia, preterm birth or most other pregnancy and delivery outcomes.
Researchers also found no evidence that the strength-training program increased miscarriages, preterm births or other adverse events. No adverse events were linked to the intervention.
The study also highlights how difficult exercise programs can be to maintain during pregnancy.
Only 48% of women with available adherence data met the study goal of at least two strength-training sessions a week, even though the program included supervised workouts and home exercise materials.
That matters because a program can only help if people are able to follow it. It also raises a practical question about how easily a supervised strength-training program could fit into routine prenatal care.
The researchers noted several other limitations. The study expected gestational diabetes to be more common than it actually was, leaving fewer cases to compare between groups. Home workouts were self-reported, so researchers could not independently verify every session. And because women knew which group they were in, some in the control group may have increased their activity on their own.
The findings also apply specifically to pregnant women with overweight or obesity who met the study criteria. They do not show that strength training prevents gestational diabetes in all pregnant women.
For now, the clearest message is that structured strength training appeared safe under the conditions of this trial and improved quality of life and pregnancy symptoms. Whether it can reliably prevent gestational diabetes remains an open question for larger studies.
The researchers reported that publication costs were supported by Fundación Miguel Servet-Navarrabiomed.