More Physical Activity May Be Needed to Lower Gestational Diabetes Risk

Is the current guidelines’ recommendation of moderate physical activity for 150 minutes per week during pregnancy enough to reduce the risk of gestational diabetes? 

Physical inactivity is associated with many complications, including an increased risk of gestational diabetes. Gestational diabetes is linked to many newborn and maternal complications, including later developing type 2 diabetes. Exercising for at least 30 minutes of moderate exercise five days a week is recommended by the physical activity guidelines. An advantage of exercising while pregnant is a lower risk of gestational diabetes. A recent meta-analysis showed the risk of gestational diabetes decreased with exercise, but many of the individual studies included did not reduce the risk of gestational diabetes.  

The study aims to examine the amount of exercise that is needed during the first trimester of pregnancy to decrease the risk of gestational diabetes. The study utilized participants who gave birth from 2013-2017 in the Pregnancy Environment and Lifestyle Study (PETALS). To evaluate exercise in this analysis, participants completed a Pregnancy Physical Activity Questionnaire, which included a sports and activity section and a section with 36 activities. The questionnaire’s sports and exercise section included ten activities that range in intensity, including walking, swimming, jogging, and weightlifting. Participants also had to fill in the duration spent performing the 36 movements. The amount of exercise was determined by the time and occurrence of the activity multiplied by the intensity (MET-hours per day). The amount of exercise was categorized into three groups. The three groups included: any vigorous exercise. This exercise meets the current recommendations with more than 7.5 MET-hours per week of moderate and vigorous exercise or meeting or exercising more than the 75th percentile with 13.2 MET-hours per week. Researchers used four different methods to assess the adjusted risk difference. The used methods were the inverse probability of treatment weighting (IPTW), targeted maximum likelihood estimation (TMLE), TMLE with defaults, and TMLE with extra learners’ defaults. 

 A total of 2,246 participants that received care from Kaiser Permanente Northern California were included in the study. Patients were excluded from the study if exercise was contraindicated during pregnancy, the amount of physical activity stated in the questionnaire was unrealistic, or they had gestational diabetes before the study visit. The average age included was 30.2 years, and 79% of participants were minorities. Five hundred sixty-one participants exercised more than 13.2 MET-hours per week, meeting or surpassing the 75th percentile, and 1685 participants exercised less than 13.2 MET-hours per week; 547 (97.5%) of the participants that completed more than 75th percentile exercised before pregnancy. 

Gestational diabetes was observed in 147 (6.5%) participants, and 26 (4.6%) of the participants with gestational diabetes met or exceeded the 75th percentile. Abnormal glucose levels were observed in 545 (24.3%) participants, and 115 (20.5%) of the abnormal screening exercised more than 13.2 MET-h per week. With the TMLE with defaults with extra learners, abnormal levels decrease by 4.8 women per 100 (95% CI 1.1, 8.5), and the risk of gestational diabetes decreases by 2.1 women per 100 [0.2, 4.1]. 

The results showed that more physical activity than the current recommendations is needed to reduce the risk of gestational diabetes. This is due to patients exercising more than 150 minutes a week not showing a decrease in risk of gestational diabetes. The study establishes that pregnant women should exercise at least 38 minutes a day during the first trimester of pregnancy to lower the risk of gestational diabetes. Carpenter and Coustan criteria were used to determine gestational diabetes, and a level greater than 140mg/dl was used for abnormal screening in this analysis. So, the results may not be generalizable for various criteria or levels that define abnormal screening. Since the use of physical activity trackers has increased, future evaluations should include physical activity trackers to evaluate physical activity along with questionnaires.   

Practice Pearls: 

• Exercise at the current recommendation of 150 minutes a week does not lower the risk of gestational diabetes. 
• The study recommends patients in the first trimester of pregnancy perform moderate exercise for at least 264 minutes each week to decrease the risk of gestational diabetes. 
• Exercising more than the current recommendation reduces the risk of gestational diabetes by 2.1 per 100 women. 

Ehrlich, Samantha F et al. “Exercise During the First Trimester of Pregnancy and the Risks of Abnormal Screening and Gestational Diabetes Mellitus.” Diabetes care vol. 44,2 (2021): 425-432. doi:10.2337/dc20-1475 

Kohli, Kamal. “Increased Exercise during First Trimester May Reduce Gestational Diabetes Risk.” Medical Dialogues. Jan 12, 2021. 

Alexis Dunn, PharmD. Candidate, Florida Agricultural & Mechanical University, College of Pharmacy and Pharmaceutical Sciences