A 2018 meta-analysis of 10 randomized trials found that inositol more than doubled the ovulation rate and made menstrual cycles more frequent in women with PCOS, compared with placebo. Evidence on pregnancy and live birth is still limited.
Relative risk 2.3. The bar is the 95% confidence interval, 1.1 to 4.7. The dashed line at 1.0 would mean no difference. Menstrual cycle frequency was also higher: relative risk 6.8, 95% confidence interval 2.8 to 16.6. Ten randomized trials. Pundir et al., BJOG, 2018.
What the trials measured
Pundir and colleagues pooled 10 randomized trials of inositol as an ovulation-support agent in women with PCOS, published in BJOG in 2018. In total, 362 women took inositol (257 took myo-inositol and 105 took D-chiro-inositol), 179 took placebo, and 60 took metformin.
Compared with placebo, inositol improved the ovulation rate (relative risk 2.3, 95% confidence interval 1.1 to 4.7) and increased how often menstrual cycles came (relative risk 6.8, 95% confidence interval 2.8 to 16.6). The authors concluded that inositol appears to regulate menstrual cycles, improve ovulation, and induce metabolic changes in PCOS.
Pregnancy and live birth
Only one trial in the review reported clinical pregnancy against placebo, and none reported live birth, so the authors called for a larger multicentre trial. A 2018 Cochrane review of inositol before IVF also rated its evidence low to very low quality, and was uncertain about live birth and clinical pregnancy.
Why it is on conception labels
PCOS is one of the most common causes of irregular ovulation, and ovulation is the first step in conceiving. That is why myo-inositol is one of the most common ingredients in conception formulas for women, often next to cycle botanicals such as vitex.
Trial doses were measured in grams, so check the amount on the label. If cycles stay irregular for several months, a clinician can check for PCOS.
Sources
This note uses the published abstract of the meta-analysis and the Cochrane summary. Doses and inositol forms varied across trials.
This is general information, not medical advice. All research.