Oocyte donation: the role of endometrial receptivity.

Sixteen patients, 15 with primary ovarian failure and one carrier of chromosomal abnormality, received 21 embryo transfers following in-vitro fertilization of donated oocytes. Hormone replacement therapy was given to mimic a natural menstrual cycle. Five pregnancies were achieved (four infants delivered and one early pregnancy loss). All patients had endometrial biopsies taken in a preceding cycle of hormone replacement therapy. The majority (61%) showed delayed maturation compared with the expected appearances for the day of the cycle as assessed on light microscopy. Patients who conceived had a significantly better endometrial response than those who did not. Five out of seven patients (71%) conceived when the endometrium was 'in phase' (less than 2 days' delay). This suggests that endometrial receptivity is a key factor in conception. The implications for improving outcome from in-vitro fertilization treatment are discussed.