Anthropometrics of neonates born to mothers with PCOS with metformin or placebo exposure in utero

Introduction Fetal growth may be affected by both maternal polycystic ovary syndrome (PCOS) and metformin therapy. Here, we explore the effect of intrauterine metformin exposure on birth anthropometrics of infants born to women with PCOS. We also investigated whether the effect of metformin on birth anthropometrics is modified by maternal pre‐pregnancy body mass index, PCOS hyperandrogenic phenotype, serum androgen levels, preconception use of metformin and offspring sex. Additionally, we assessed newborn anthropometrics in relation to a national reference population. Material and methods Individual data from three randomized controlled triasl were pooled. The randomized controlled trials investigated the effects of metformin in pregnant women with PCOS. In all, 397 and 403 were randomized to the metformin and placebo groups, respectively. A Scandinavian growth reference was used to calculate sex and gestational age adjusted z‐scores. Linear regression models were used to estimate the effect of metformin on offspring z‐scores of head circumference, birth length, birthweight, placental weight, body mass index, ponderal index and birthweight:placental weight ratio. S‐testosterone, s‐androstenedione, and s‐sex‐hormone binding globulin from four timepoints in pregnancy were analyzed. Results Compared with the PCOS‐placebo group, newborns in the PCOS‐metformin group had larger head circumference (head circumference z‐score: mean difference = 0.25, 95% CI = 0.11– 0.40). This effect of metformin on head circumference z‐score was particularly observed among offspring of overweight/obese mothers and mothers with hyperandrogenic PCOS‐phenotype. We observed no difference in other anthropometric measures between the metformin and placebo groups or any clear interaction between maternal androgen levels and metformin. Newborns in the PCOS‐placebo group were shorter than in the reference population (birth length z‐score: mean = −0.04, 95% CI = –0.05 to −0.03), but head circumference and birthweight were similar. Conclusions Larger head circumference was observed at birth in metformin‐exposed offspring of mothers with PCOS. PCOS‐offspring were also shorter, with a similar birthweight to the reference population, indirectly indicating higher weight‐to‐height ratio at birth. We explored the effect of metformin vs placebo on newborn anthropometrics born to women with PCOS, and found that newborns exposed in utero to metformin compared with placebo had larger head circumferen