Objective: To compare the effects of fresh embryo transfers (ET) and elective frozen/thawed embryo transfers (eFET) on implantation, clinical pregnancy, and live birth rates in poor ovarian responders, as defined by the Bologna criteria.
Materials and methods: All electronic databases of embryo transfers between January 2011 and January 2014 were retrospectively reviewed. Two hundred fifty-nine of all the fresh ET and 96 of all eFET were included into the study. An antagonist protocol with letrozole was used for the controlled ovarian hyperstimulation (COH) in all participants.
Results: The mean age was 36.9 years (range, 21-43 years) in the fresh ET arm and 37.2 years (range, 21-43 years) in the eFET arm (p=0.45). The clinical pregnancy rate was 35% (90/259) versus 29% (28/96); the abortion rate was 27% (20/75) versus 36% (9/25); and the live birth rate was 21% (55/259) versus 17% (16/99). There were no significant differences between groups and p values were 0.32, 0.52, and 0.42, respectively. The mean E2 level was 389 (range, 50-2055 pg/mL) in the fresh ET group (on hCG day) and 418 pg/mL (range, 121-3073 pg/mL) in the eFET group (on day 14 of cycle) (p=0.122). No differences were found between the two groups with respect to the total number of retrieved oocytes (p=0.55) and number of metaphase II (MII) oocytes (p=0.81). The number of embryo transfers was statistically different (p=0.005). The effects of age, total number of retrieved oocytes, number of MII oocytes, type of treatment, number of ET, and the day of ET and E2 level to live birth outcomes were investigated using binary logistic regresion analyses, and no stastical effect was determined by any of the parameters. P values were p=0.50, 0.66, 0.45, 0.30, 0.30, 0.08, and 0.90, respectively.
Conclusion: E2 levels tend to be lower in poor responders, thus the receptivity of the endometrium may be damaged less than normal, which may explain why pregnancy results are the same between eFET and ET groups.
Keywords: Frozen embryo transfer; Poor responder; endometrial receptivity.