Daily myo-inositol supplementation in pregnancy was not found to reduce the risk of severe complications like gestational diabetes, preeclampsia, or preterm delivery in polycystic ovarian syndrome (PCOS) women, according to a recent study published in JAMA. The research concluded that myo-inositol, in spite of previous indications of its possible usefulness, had no notable impact in avoiding these events. The study was conducted by Anne W. and colleagues.
PCOS is a prevalent endocrine disorder in women of childbearing age and is highly correlated with increased risks of pregnancy complications. Pregnant women with PCOS have a higher likelihood of gestational diabetes, preeclampsia, and preterm birth. Myo-inositol, a nutritional supplement, has been extensively investigated for its potential in enhancing insulin sensitivity and ovarian function. Earlier small studies had indicated potential advantages in lowering pregnancy complications but were not done on a large scale using randomized controlled trials. This trial, which was performed in 13 hospitals in the Netherlands, sought to settle whether myo-inositol supplementation could offer quantifiable protection during pregnancy.
The study was set up as a double-blind, placebo-controlled, randomized trial and involved 464 pregnant women with PCOS. Participants were recruited from June 2019 to March 2023, with last follow-up being finished in December 2023. They were divided at random in a 1:1 ratio to receive either myo-inositol (2 g with 0.2 mg folic acid twice daily, n = 230) or placebo (0.2 mg folic acid only, n = 234) until delivery. The main outcome was a composite of gestational diabetes, preeclampsia, or preterm delivery before 37 weeks' gestation.
Results
Mean participant age was 31.5 years, with a high percentage identifying as White (86.1%, n = 395) and a smaller percentage as Asian (3.9%, n = 18).
Biochemical hyperandrogenism occurred more frequently at baseline in the myo-inositol group (29.0%, n = 53 of 180) than in the placebo group (18.5%, n = 37 of 193).
A primary outcome event was observed in 25.0% (n = 56) of patients treated with myo-inositol and in 26.8% (n = 61) of those treated with placebo.
This corresponded to a relative risk of 0.93 (95% CI, 0.68–1.28; P = 0.67), showing no statistically significant difference between both groups.
This randomized controlled trial showed that myo-inositol supplementation in pregnancy did not have any important effect on the prevention of gestational diabetes, preeclampsia, or preterm delivery in PCOS women. While safe and well-tolerated, myo-inositol should not be regarded as an effective means of prevention of pregnancy complications in this population.
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. Published online September 08, 2025. doi:10.1001/jama.2025.13668
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