Role of corpus luteum function in embryo implantation.

The present study was undertaken to evaluate the role of corpus luteum function in the implantation process of cryopreserved embryos. Six patients with tubal infertility were studied, with a total of 27 fresh embryos being replaced following controlled ovarian hyperstimulation and in vitro fertilization. These embryo transfers failed to produce pregnancy. From the patients, 22 supernumerary embryos were cryopreserved and 10 viable frozen-thawed embryos were transferred in a subsequent natural cycle, resulting in 2 pregnancies. In 1 of the pregnancies, the serum concentrations of estradiol (E2) and progesterone (P4) in the midluteal phase were 29 pg/ml and 5.6 ng/ml, respectively. These values were considered to be below the physiological range. These data suggest that a pregnancy can be achieved in spite of low circulating E2 and P4 levels during the luteal phase, which are generally indicative of the luteal phase defect.