Interventions to prevent women from developing gestational diabetes mellitus: an overview of Cochrane Reviews.

Overview of Cochrane systematic reviews evaluating interventions to prevent gestational diabetes mellitus in pregnant women. Included studies were randomized trials in general obstetric populations, with some trials enrolling women at higher risk such as those with overweight or obesity.

Pregnancy interventions included omega-3 fatty acids (0.22 to 2.8 g/day), myo-inositol (2 to 4 g/day), vitamin D alone or with calcium or other micronutrients (weekly total 1400 IU to 30,000 IU), and probiotics, generally started in mid-pregnancy and continued for the remainder of gestation when given. Several trials tested supplementation alongside dietary advice or other lifestyle measures.

Overall, no preventive intervention showed clear benefit or harm across the included reviews. Among supplement strategies, myo-inositol reduced gestational diabetes risk in small trials (RR 0.43, 95% CI 0.29 to 0.64) and vitamin D also showed a possible benefit (RR 0.51, 95% CI 0.27 to 0.97), while omega-3 fatty acids showed no effect (RR 1.02, 95% CI 0.83 to 1.26). Probiotics combined with dietary intervention were promising in single small comparisons (RR 0.37, 95% CI 0.15 to 0.89; RR 0.38, 95% CI 0.16 to 0.92), but the evidence base was limited. The authors concluded that more high-quality randomized trials are needed, including better reporting and studies begun before conception or between pregnancies.

The evidence was heterogeneous across interventions, populations, doses, and timing, and many findings came from small or single trials. Several comparisons had wide confidence intervals or low-quality evidence, limiting certainty about benefit or harm. Arm-level details such as demographics and dosing were inconsistently reported, and some interventions were studied mainly in specific regions such as Asia.