Please cite this paper as: Vanky E, Nordskar J, Leithe H, Hjorth-Hansen A, Martinussen M, Carlsen S. Breast size increment during pregnancy and breastfeeding in mothers with polycystic ovary syndrome: a follow-up study of a randomised controlled trial on metformin versus placebo. BJOG 2012;119:1403–1409.
Objective To study the significance of breast size increment in pregnancy, and the impact of metformin during pregnancy on breastfeeding in women with polycystic ovary syndrome (PCOS).
Design A follow-up study of a randomised controlled trial (the PregMet study).
Setting Eleven secondary care centres.
Population Women with PCOS during pregnancy and postpartum.
Methods Women with PCOS were randomised to treatment with metformin or placebo from the first trimester to delivery. Questionnaires were sent to 240 participants 1 year postpartum: 186 responded.
Main outcome measures Pre-pregnancy and late-pregnancy brassiere size and breastfeeding patterns were registered, and androgen levels were measured in the mothers.
Results No difference in breast size increment and breastfeeding were found between the placebo and metformin groups. Breast size increment correlated positively with the duration of both exclusive and partial breastfeeding, whereas body mass index (BMI) correlated negatively with the duration of partial breastfeeding. Dehydroepiandrostenedione-sulphate (DHEAS), testosterone and free testosterone index (FTI) in pregnancy did not correlate with breast size increment or duration of breastfeeding. Women with no change in breast size were more obese, had higher blood pressure, serum triglycerides and fasting insulin levels, and had a shorter duration of breastfeeding compared with those with breast size increment.
Conclusions Metformin and androgens had no impact on breastfeeding. Women with PCOS who had no breast size increment in pregnancy seem to be more metabolically disturbed and less able to breastfeed.