Serum anti-Müllerian hormone levels in women are unstable in the postpartum period but return to normal within 5 months: a longitudinal study

Anti-Mullerian hormone (AMH) levels fall during pregnancy but the amount of time required for AMH levels to return to normal has not been accurately determined. We have previously shown that AMH levels have yet to return to normal in some women at 3-months postpartum. In this study, AMH levels were examined at 1- and 5-months postpartum to examine whether AMH levels had returned to normal within this interval. Longitudinal study involving 38 pregnant women, with serum samples taken in the first trimester, third trimester, 1-month postpartum, 5-months postpartum and 4–6 years postpartum. Participants were recruited from a tertiary maternity clinic (single centre). All women in the study were intending to breastfeed exclusively for at least 5 months, with all 38 participants achieving this at 1-month postpartum and 36/38 after 5 months. Serum AMH concentrations had not returned to expected non-pregnant levels by 1-month postpartum. At 5-months postpartum, mean AMH concentrations were similar to expected non-pregnant levels but the rank order of AMH concentrations was still dissimilar to the non-pregnant state. The regulation of AMH secretion appears to be distinctly different in non-pregnant, pregnant and postpartum populations. This may affect the conclusions that can be drawn from AMH measurements in women during pregnancy and the postpartum period.