The ability to control human fertility has changed completely in the last half century, from the development of reliable contraceptive methods to assisted reproduction. The assessment of an individual’s fertility, however, has progressed remarkably little in the last several decades. While the reproductive potential of both men and women is predicated on successful production of gametes, the likelihood of conception in women (or ‘fecundability’) is primarily determined by the release of a single egg each month. Conversely, in men it is based on the continuous production of large numbers of motile sperm with the ability to traverse the female reproductive tract and successfully fertilise that egg. Assessment of infertility therefore focuses on ovulation, spermatogenesis, and the patency of the fallopian tubes. The assessment of ovulation is now complemented by the ability to assess aspects of how many follicles the ovary contains (the ovarian reserve) through the measurement of circulating anti-Müllerian…