Relative contribution of advanced age and reduced follicle pool size on reproductive success the quantity–quality enigma

Introduction to reproductive aging It is a well-known phenomenon that as a woman becomes older, her chances of reproductive success decrease. This is largely attributed to ovarian aging, the age-related decline in the quantity and quality of oocytes in the ovaries. At birth every woman has a certain endowment of oocytes. This number of oocytes decreases at various rates during life until the ovarian reserve is exhausted and menopause is reached [1]. Renewal of the oocyte pool from pluripotent stem cells has so far been denied, but recent studies have elicited possible new insights into this field [2]. The gradual decline in oocyte quantity with age is accompanied by a decrease in oocyte quality. This is substantiated by decreased pregnancy rates, increased miscarriage rates, and an increase in the rate of aneu-ploidy leading to offspring with trisomic karyotypes [3, 4]. Also, a growing incidence of unexplained infertility is apparent in women trying to achieve a pregnancy at a more advanced age [5]. The age related decrease in female fertility has direct repercussions in Western societies, as the trend to delayed childbearing continues. The introduction of effective contraceptive methods in the 1960s and the growing participation of women in the labor force has resulted in a major change in reproductive behavior [6]. The average age at the birth of the first child has increased from approximately 24 years of age in 1970 to the age of 30 or over in recent years [7, 8]. In addition, the completed fertility rate (number of children born per woman) has decreased considerably and a growing proportion of women seek the help of assisted reproductive technology (ART) to conceive. As modern infertility treatments can only help around 50% of these women, a considerable proportion of women will remain childless involuntarily, with increased levels of personal distress and grave effects on relationship stability [9, 10]. The continuing trend to delay childbearing does not only have a large impact on population demographics; the annual costs for society from infertility treatments and ART-related complications, such as multiple pregnancies, are also high [11, 12].