Hvidman HW, et al. – The objectives of this study are to examine the relationship between anti–Müllerian hormone (AMH), a well–established marker of the ovarian reserve, and time–to–pregnancy (TTP) in natural conceptions, and to evaluate changes in serum–AMH in early pregnancy. TTP was unrelated with z–AMH when modelled as a continuous covariate. Unexpectedly, TTP was shorter in the low z–AMH group. Natural conception was seen in women with a wide range of AMH–levels including women with undetectable serum–AMH. A continuous decrease in serum–AMH was seen amid first and second trimester. Preconception OC–use was distinguished as an independent predictor of a prolonged TTP, and the duration of OC–use seemed to impact the delay in conception. Although this is presently one of the largest studies exploring the relationship amongst AMH and fecundability in fertile women, the study has some limitation including a relatively low participation rate and a risk of selection bias in addition to AMH evaluation in pregnancy and a retrospective collection of TTP and OC–use related to a risk of recall bias. These limitations may clarify the unexpected finding of a shorter TTP in the low z–AMH group.