Luteal phase progesterone and oestradiol after ovarian stimulation: relation to response and prediction of pregnancy.

Research has focused on optimizing luteal phase support and endometrial receptivity in ovarian stimulation cycles. In this study, serial endocrine measurements were taken in 600 patients after a gonadotrophin-releasing hormone antagonist stimulation protocol. On the day of blastocyst transfer, serum progesterone and oestradiol were similar irrespective of a subsequent positive or negative pregnancy test (median 99 ng/ml versus 103 ng/ml for progesterone, respectively) or a subsequent live birth or pregnancy loss. Serum progesterone was significantly correlated to each ovarian response parameter (total number of follicles, number of oocytes retrieved and oestradiol concentration; r = 0.45, 0.57 and 0.54 respectively, all P < 0.0001). These correlations were consistent irrespective of clinical outcome. On the day of the pregnancy test, these correlations had vanished except in the live birth subgroup showing a weaker correlation (r = 0.22, 0.27 and 0.32 respectively, all P < 0.005). The lowest HCG and progesterone levels associated with live birth were 59.3 IU/l and 12.3 ng/ml, respectively. Fourteen out of 92 patients (15.2%) with pregnancy loss had normal HCG but low progesterone levels (above and below their respective 5th percentile), and miscarried before the end of the 7th week, when the luteal-placental shift occurs.