Oocyte donation: the role of endometrial receptivity M.C.Davies1, M.C.Anderson2, B.A.Mason3 and

'To whom correspondence should be addressed 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 ' (<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. Key words: donor gametes/endometrium/implantatio