Evidence of uterine inadequacy to egg implantation in stimulated in vitro fertilization cycles.

From 104 IVF cycles 166 embryos were immediately transferred (63 embryo transfers, ET), whereas 151 embryos were frozen until later transfer (77 embryo transfers). There were 8 (12.7%) or 19 (24.7%) pregnancies after fresh or frozen-thawed ET, respectively. Sixteen pregnancies (29.1%) originated from 55 ETs of frozen-thawed embryos coming from IVF cycles in which pregnancy was not induced by fresh ET. The pregnancy rate after fresh ET (10.5%) was lower than that obtained when the same patients received frozen-thawed embryos (27.1%, P less than 0.02). It is concluded that a normal pregnancy rate may result if the embryos originating from an unsuccessful IVF-ET cycle are transferred in a favorable uterus.