Myo-Inositol

Claimed to restore ovulation and improve fertility in polycystic ovary syndrome, improve insulin sensitivity, prevent gestational diabetes, reduce anxiety and panic and aid weight loss in PCOS. Every outcome in the Cochrane PCOS review is low or very low certainty. Across 13 trials and 1,472 subfertile women, live birth was OR 2.42 (95% CI 0.75–7.83) from two trials and only 84 women, clinical pregnancy OR 1.27 (0.87–1.85) with no clear difference, and the one significant result — miscarriage OR 0.40 (0.19–0.86) — rests mainly on a single trial with an unusually high control-group miscarriage rate, and removing that trial eliminated the effect. The reviewers state they are uncertain whether myo-inositol improves live birth or clinical pregnancy rates.

The gestational-diabetes review looks more impressive and should be read more carefully: gestational diabetes RR 0.53 (0.31–0.90), hypertensive disorders RR 0.34 (0.19–0.61) and preterm birth RR 0.35 (0.17–0.70), from seven trials and 1,319 women of which six were Italian and one Irish, with GRADE certainty for the primary maternal outcomes low to very low. Halving gestational diabetes and cutting hypertensive disorders and preterm birth by two-thirds are implausibly large effects for a dietary polyol and are exactly the pattern small single-centre trials produce. Gestational weight gain was −0.25 kg (95% CI −1.26 to 0.75) — no weight effect.

Safety knowledge is limited: the exposure base is dominated by short pregnancy and peri-conception trials in small Italian cohorts, the Cochrane PCOS review could not assess harms at all because adverse-event reporting was too poor to pool, and the gestational-diabetes review found neonatal hypoglycaemia RR 3.07 (0.90–10.52) at very low certainty — a possible harm whose confidence interval cannot exclude a threefold increase and which should not be dismissed as null merely because it missed significance. No hepatotoxicity signal; no upper intake level located.