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Pregnancy wastage and reproductive aging: the oocyte donation model.

Women are most successful in achieving pregnancy and delivering a healthy child when in their twenties. Natural selection against conception contributes to pregnancy wastage as women age. This phenomenon is principally a result of detrimental changes occurring within the pool of available oocytes. Oocyte donation provides a unique opportunity to study the effect of individual components of the reproductive tract by isolating the uterus from the gamete. When oocytes from young women are used to create embryos for transfer to older recipients, implantation and pregnancy rates mimic those seen in younger individuals. Furthermore, following oocyte donation, the number of miscarriages and chromosomal anomalies dramatically decreases, implying that the uterus is not responsible for the poor outcomes normally experienced by women of advanced reproductive age.