Vitamin D supplementation before in vitro fertilisation in women with polycystic ovary syndrome: multicentre, double blind, placebo controlled, randomised clinical trial.

ObjectiveTo evaluate whether vitamin D supplementation improves live birth rates in women with polycystic ovary syndrome undergoing in vitro fertilisation.DesignMulticentre, double blind, placebo controlled, randomised clinical trial.Setting24 fertility centres in China.Participants876 participants with polycystic ovary syndrome undergoing in vitro fertilisation.InterventionsParticipants were randomised (1:1) to receive vitamin D 4000 IU/day or placebo before in vitro fertilisation for up to 90 days until the trigger day.Main outcomes measuresThe primary outcome was live birth after the first embryo transfer. Secondary outcomes included serum 25-hydroxyvitamin D (25-OHD) levels on trigger day, pregnancy outcomes, fertility outcomes, and adverse events including severe ovarian hyperstimulation syndrome.ResultsOf 876 participants randomised, 865 were included in the modified intention-to-treat analysis, with 435 in the vitamin D group and 430 in the placebo group. Baseline mean serum 25-OHD levels were 16.5±7.2 and 16.1±6.7 ng/mL in the vitamin D and placebo groups, respectively. On the day of triggering, the serum 25-OHD level was significantly higher in the vitamin D group than in the placebo group (32.3±11.2 v 18.2±7.6 ng/mL, adjusted mean difference 13.6, 95% confidence interval 10.9 to 16.3). 226 (52.0%) live births occurred in the vitamin D group and 216 (50.2%) in the placebo group (adjusted risk ratio 1.03, 95% confidence interval 0.91 to 1.18). Severe ovarian hyperstimulation syndrome occurred in three and six participants in the vitamin D and placebo groups, respectively (adjusted risk difference -0.7%, 95% confidence interval -2.0% to 0.6%).ConclusionsAlthough vitamin D supplementation (4000 IU/day) for up to 90 days increases serum 25-OHD levels, this does not translate to improved live birth rates after the first transfer for patients with polycystic ovary syndrome.Trial registrationClinicalTrials.gov NCT04082650.