Pre-Pregnancy Physical Activity Lowers Risk of Diet-Controlled but Not Insulin-Treated Gestational Diabetes Mellitus: A Korean Prospective Cohort Study.

BACKGROUND: Gestational diabetes mellitus (GDM) presents clinically as either diet-controlled (diet-controlled gestational diabetes mellitus, A1GDM) or medication-controlled (insulin-requiring gestational diabetes mellitus, A2GDM) subtypes. Pre-pregnancy physical activity represents a significant modifiable factor in GDM prevention and management. Therefore, this study aimed to investigate the differential effects of physical activity on these two clinical GDM subtypes. METHODS: This secondary analysis utilized data from the Korean Pregnancy Outcome Study, a longitudinal multicenter cohort. From 3,457 singleton pregnant participants, physical activity was assessed at five time points from pre-pregnancy to postpartum using the International Physical Activity Questionnaire Short Form. Logistic regression models were used to estimate adjusted odds ratios (aORs) for GDM subtypes according to physical activity. Firth's penalized logistic regression was used for A2GDM analysis. RESULTS: Of the participants, 231 developed GDM (overall prevalence 6.7%). Among these cases, 198 (85.7%) were diagnosed with A1GDM, and 33 (14.3%) with A2GDM. No significant differences in moderate-to-vigorous physical activity or muscle-strengthening activity were observed across three groups in baseline characteristics. However, Women who performed muscle-strengthening activity before pregnancy had a significantly lower risk of A1GDM (aOR, 0.492; 95% confidence interval, 0.262-0.923), with risk decreasing as activity frequency increased (P for trend = 0.014). CONCLUSION: Pre-pregnancy muscle-strengthening activity is associated with significantly reduced risk of A1GDM. These findings highlight the importance of muscle-strengthening activity before conception as a potential strategy for GDM prevention.