The timing for initiating estrogen stimulation in artificial cycle for frozen-thawed embryo transfer can be flexible

Abstract Background There remains a lack of evidence to demonstrate whether the initiation time estrogen stimulation is flexible in proliferative endometrial phase during artificial cycle for frozen-thawed embryo transfer (AC-FET). Methods FET records were retrospectively reviewed from large university-affiliated reproductive medicine center. Only patients who undergoing their first with single blastocyst AC-FET cycles included: thereby 660 recruited, and grouped according day usage as early group (estrogen initiated days 2–5 menses, n = 128) late on or after 6th 532). The primary outcome was ongoing pregnancy rates (OPR). Results biochemical clinical pregnancies significantly higher relative those group, however, no significant differences noted between two groups OPR. Furthermore, adjusting results potential confounders, impact observed Conclusions This study provides that initiating menses do not exert adverse effects OPR AC-FETs. Thus, can be scheduled manner without compromising outcomes.