Maternal and fetal insulin levels at birth in women with polycystic ovary syndrome: data from a randomized controlled study on metformin.

CONTEXT: Metformin is suggested to reduce pregnancy complications in women with polycystic ovary syndrome (PCOS). Metformin crosses the placenta and therapeutic concentrations are measured in the fetal circulation. Whether metformin treatment in pregnant PCOS women affects maternal and fetal insulin concentrations at birth is not clarified.

OBJECTIVES

To investigate the possible effect of metformin on insulin concentrations in umbilical cord blood and the possible association between maternal and fetal insulin concentrations.

DESIGN

Post-hoc analysis of a subgroup of PCOS women participating in a double-blind randomized controlled trial.

SETTING

University hospital setting.

PARTICIPANTS

Women with PCOS (n=118), aged 19-39 years.

MAIN OUTCOME MEASURES: Maternal and umbilical cord insulin concentrations immediately after birth.

RESULTS

At delivery women randomized to metformin had lower insulin concentrations than those randomized to placebo (259±209 vs 361±261 pmol/l; P=0.020). No difference was found in insulin concentrations in umbilical venous (P=0.95) and arterial (P=0.39) blood between the metformin and placebo groups. The arteriovenous difference was also equal between the groups (P=0.38). Insulin concentrations were higher in the umbilical vein than in the umbilical artery independent of randomization (70±51 vs 45±48 pmol/l; P<0.0005).

CONCLUSIONS

In PCOS, metformin treatment during pregnancy resulted in lower maternal insulin concentrations at delivery. Metformin treatment did not affect fetal insulin concentrations. Higher insulin concentrations in the umbilical vein indicate that the placenta somehow secretes insulin to the fetus. The possibility of placental insulin secretion to the fetus deserves further investigations.