Progesterone (P) and estradiol (E2) are required for successful conception, both to prepare the endometrium for blastocyst implantation and pregnancy. During IVF-ET, controlled ovarian hyperstimulation results in excessive follicular development and supraphysiologic serum concentrations of E2 and P. Such derangements raised concerns about the impact of such abnormalities on the luteal phase and a possible adverse impact on endometrial tissue [1-3]. E2 initiates hypertrophy and hyperplasia of endometrial epithelia, but its role in the luteal phase remains poorly understood. How E2 influences endometrial synchronization and blastocyst implantation is also not well described [4-6]. In contrast, the role of P in the luteal phase is better examined Csapo et al [7,8] showed that luteectomy leads to miscarriage in almost every case if performed before seven weeks of gestational age. P transforms the E2-prepared endometrium into a secretory tissue and creates a hospitable environment for embryo attachment [9].
Although previous research has established that E2 and P regulate events leading to implantation, relatively little is known about their relative proportion in maternal serum during the early luteal phase. In the present study, we retrospectively compared the E2/P ratio in the luteal phase in women undergoing superovulation for IVF-ET who had a successful implantation with those who failed to conceive after such treatment.
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