The study enrolled 464 pregnant women diagnosed with PCOS between 8 and 16 weeks of gestation across 13 hospitals in the Netherlands between June 2019 and March 2023. Participants were randomly assigned to receive either myo-inositol (2 g) combined with 0.2 mg folic acid twice daily or a placebo containing only 0.2 mg folic acid until delivery. The average age of the participants was 31.5 years.
The key findings were as follows:
- 25% of women in the myo-inositol group experienced at least one primary outcome—gestational diabetes, preeclampsia, or preterm birth.
- 26.8% of women in the placebo group experienced similar outcomes.
- The difference between the two groups was not statistically significant (relative risk, 0.93).
- Myo-inositol supplementation did not show any measurable advantage over placebo in reducing pregnancy complications.
The authors concluded that taking myo-inositol during pregnancy does not help in preventing these complications in women with PCOS. Therefore, they advised against recommending myo-inositol supplementation as a preventive measure during pregnancy in this population.
While earlier studies had suggested potential benefits of myo-inositol in improving insulin sensitivity and reducing the risk of gestational diabetes, the findings of this large, well-designed trial did not support those assumptions.
The study had a few limitations. The myo-inositol group showed a higher baseline prevalence of biochemical hyperandrogenism than the placebo group, though this appeared random and did not influence outcomes. The overall rate of pregnancy complications was lower than expected, likely due to healthier participant characteristics. Additionally, adherence to supplement intake was modest, with only about one-third of participants in each group consuming at least 80% of their prescribed doses.
The authors emphasized that the prevention of pregnancy complications in women with PCOS remains a critical research priority. Despite the negative findings, they highlighted the importance of continued investigation into other potential interventions to improve pregnancy outcomes in this high-risk group.
"Daily supplementation with myo-inositol at a dose of 4 g per day did not improve pregnancy outcomes and should not be considered as part of dietary recommendations for pregnant women with PCOS," the authors concluded.
Reference:
van der Wel AWT, Frank CMC, Bout-Rebel R, et al. Myo-inositol Supplementation to Prevent Pregnancy Complications in Polycystic Ovary Syndrome: A Randomized Clinical Trial. JAMA. 2025;334(13):1151–1159. doi:10.1001/jama.2025.13668
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