Active corpus luteum function at pre-, peri- and postimplantation is essential for a viable pregnancy.

Luteal-phase estrogen and progesterone concentrations were measured every other day and used to monitor the corpus luteum activity. The patterns of estrogen and progesterone concentrations were compared relative to the day of endogenous human chorionic gonadotropin (hCG) detection (defined as the day of implantation). The relationship between estrogen and progesterone and hCG concentrations was studied in 71 viable pregnancies, 12 clinical abortions, five preclinical abortions and 84 non-pregnant cycles after IVF/ET. Although all patients received luteal-phase progesterone support (25-50 mg/ml), low late luteal-phase progesterone concentrations of < 30 ng/ml from day + 11 to day + 15 were found in 64 patients (17% of viable pregnancies, 33.3% of clinical abortions, 60% of preclinical abortions and 53.6% of non-pregnant cycles) day + 1 was the day of retrieval). Implantation always occurred before or on day + 13 and 86% of pregnant cycles implanted on day + 8 to day + 11. Viable pregnancies had significantly higher mean progesterone concentrations on day + 3 to day + 7 (pre-implantation) and on day + 9 to day + 15 (postimplantation) than those of non-pregnant cycles or abortions. On the day of implantation, the mean +/- standard of deviation of estrogen (pg/ml) and progesterone (ng/ml) levels for viable pregnancies, clinical abortion and preclinical abortions were 314 +/- 210, 40.5 +/- 25; 226.7 +/- 246, 48.7 +/- 31; and 39.6 +/- 24.5, 28.6 +/- 24.5, respectively. On the same day, 73.2% of viable pregnancies, 41.7% of clinical abortions, and 20% preclinical abortions had a progesterone concentration > 30 ng/ml; 73.2% of viable pregnancies, 41.7% of clinical abortions and 20% of preclinical abortions had an estrogen concentration > 100 pg/ml. Although not precluding implantation completely, late luteal-phase hormonal deficiencies may impair endometrial growth and might ultimately lead to failure or abnormal implantation. A viable pregnancy requires not only a functional corpus luteum in the early luteal phase to develop a receptive endometrium, but also a responsive corpus luteum in the late luteal phase to support pregnancy. The time of implantation is critical. Implantation that occurs before the demise of the corpus luteum will facilitate a normal pregnancy.