Objective: To assess the comparative contribution of endometrial and oocytic aging to the decline in fertility with age.
Design: Retrospective analysis of conception and abortion rates in an egg donation program, with respect to donor and recipient ages.
Patients: All oocyte recipients had ovarian failure. Donors were women undergoing in vitro fertilization who contributed up to a third of retrieved oocytes.
Interventions: None.
Results: Thirty pregnancies (28 intrauterine) were recorded in 169 reception cycles originating from 91 donation cycles. Women who conceived were younger than those who did not (median age 31 versus 37; P less than 0.046), with no difference in age of donors. There was a significant difference in spontaneous abortion rate by age of donor rather than by age of recipient. Donors to successful pregnancies were younger than donors to aborted pregnancies (median age 27.5 versus 33; P less than 0.0211), but the 11 women with aborted pregnancies did not differ in age from the 17 women with successful pregnancies.
Conclusions: In women, endometrial function as expressed by conception rate in the recipients declines with age, whereas it is oocyte age that primarily influences risk of abortion.