Abstract
BackgroundFrozen embryo transfer (FET) can greatly improve the pregnancy outcomes for high responder patients. However, it is not known whether the timing of FET is a risk factor on pregnancy outcomes in high responder patients undergoing freeze-all cycles.MethodsA retrospective cohort study to compare the pregnancy outcomes of the immediate and delayed FET groups in high responder patients undergoing freeze-all cycles. The two groups were defined as that FET took place either within the first menstrual cycle following oocyte retrieval or afterwards. Propensity score matching was used to make the potential risk factors of the two groups comparable. Multivariable regression analysis was used to study the effect of the timing of FET on pregnancy outcomes in the entire cohort and propensity score-matched cohort, even in different controlled ovarian hyperstimulation protocol cohorts as subgroup analysis.ResultsWe obtained 1130 patients in immediate FET group and 998 patients in delayed FET group, and the average age of the two groups were 30.30 and 30.63. We showed that the immediate FET group were equivalent to delayed FET group in the entire cohort [clinical pregnancy rate (CPR), 61.0% versus 63.4%, adjusted odd ratio (OR), 0.939, 95% confidence interval (CI), 0.781–1.129; spontaneous abortion rate (SAR), 10.1% versus 12.6%, adjusted OR, 0.831, 95% Cl (0.628–1.098); live birth rate (LBR), 49.9% versus 49.2%, adjusted OR, 1.056, 95% Cl (0.883–1.263)]. The same results were obtained by χ2 test in the propensity score-matched cohort (CPR, 60.5% versus 63.5%; SAR, 11.6% versus 12.3%; LBR, 48% versus 49.3%) (P > 0.05). Subgroup analysis indicated that pregnancy outcomes of immediate FET were no difference to delayed FET in gonadotropin-releasing hormone agonist (GnRH-a) protocol (P > 0.05). The SAR of the immediate FET group were lower than that of the delayed FET group in GnRH antagonist protocol (adjusted OR, 0.645, 95% CI, 0.430–0.966) (P < 0.05), no differences were observed in CPR and LBR (P > 0.05).ConclusionsThe pregnancy outcomes of immediate FET were no difference to delayed FET in high responder population undergoing freeze-all cycles.
Highlights
Frozen embryo transfer (FET) can greatly improve the pregnancy outcomes for high responder patients
It is unclear whether the detrimental effects on endometrial receptivity caused by Controlled ovarian hyperstimulation (COH) would be sustained over a long period of time, up to the subsequent menstrual cycle, especially in patients with High ovarian response (HOR) who are most affected by COH
Study population and design We conducted a retrospective cohort study including all patients from January 2015 to March 2019 at our reproductive medicine center and the study was conducted in accordance with ethical standards (2020PS006F); informed consent was obtained from all subjects
Summary
Frozen embryo transfer (FET) can greatly improve the pregnancy outcomes for high responder patients. Postponement of FET may increase the anxiety of patients [10]; in the immediate FET cycle, poor endometrial receptivity or physical condition may not be fully recovered to the pre-stimulation state, which may affect pregnancy outcomes [11]. It is unclear whether the detrimental effects on endometrial receptivity caused by COH would be sustained over a long period of time, up to the subsequent menstrual cycle, especially in patients with HOR who are most affected by COH. The use of different gonadotropin-releasing hormone (GnRH) analogues in the process of COH act on the pituitary in different ways [12], and it is controversial whether the timing of FET affects pregnancy outcomes in different COH protocols [11, 13]
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