Serum estradiol/progesterone ratio on day of embryo transfer may predict reproductive outcome following controlled ovarian hyperstimulation and in vitro fertilization.

Background: To determine whether estradiol-to-progesterone (E2/P) ratios at the time of embryo transfer (ET) have an effect on implantation and pregnancy in IVF cycles.

Methods: 239 women consecutively treated by IVF or ICSI were retrospectively analyzed and early luteal serum E2 and P were measured on the day of ET. Transfer occurred after a variable in vitro culture period ranging from 4-7 days after ovulation induction (OI). Following ET, serum E2/P ratios were calculated for clinical pregnancies, preclinical abortions and non-conception cycles.

Results: Receiver-operator curve analysis demonstrated that the E2/P ratio could differentiate between clinical pregnancies and non-pregnant cycles (area under the curve on OI +4 days = 0.70; 95% CI = 0.60-0.80; p = 0.003, on OI +5 days = 0.76; 95% CI = 0.64-0.88; p = 0.001, OI +7 days = 0.85; 95% CI = 0.75-0.96; p < 0.0001).

Conclusion: These retrospective data may hold prognostic value regarding endometrial receptivity as reflected by E2/P measurements and may help improve IVF treatment outcome. Further prospective studies should be undertaken to confirm these obersveration.