19 - Screening for early ovarian ageing

Summary

Introduction

Ovarian ageing is thought to be caused by a decrease in the number of primordial follicles and/or a decline in the quality of the oocytes within them. Oocyte numbers within the fetal ovary peak at 20 weeks of gestation, subsequently falling to 1—2 million at birth. Thereafter, the rate of atresia within the oocyte pool remains relatively constant until the age of 37.5 years, when there is an accelerated diminution in oocyte numbers, which fall to around 1000 at menopause (51 years). However, incipient ovarian senescence may start many years earlier, and one in 100 women can expect to experience premature menopause before the age of 40 years. It has been suggested that there is a 13-year window between the beginning of an accelerated phase of follicular atresia (age 38 years) and menopause itself (age 51 years), during which menstrual cyclicity is maintained but fecundity is significantly reduced. Thus, a woman who enters natural menopause at the age of 45 years could have begun the process of accelerated atresia (early ovarian ageing) at the age of 32 years. It is this period of silent ovarian ageing that offers a window for appropriate screening. In this chapter, we consider the rationale for ovarian reserve testing, examine the attributes of an ideal test and review the predictive value of a number of common tests. We conclude by discussing the suitability of these tests for inclusion in a screening strategy for early ovarian ageing.