A universal freeze all strategy: why it is not warranted.
OBJECTIVE
There's some preclinical evidence of an adverse effect of multifollicular growth on endometrial function in assisted reproductive technology cycles. Universal elective frozen embryo transfer (eFET) in an unstimulated cycle is being promoted as a panacea, regardless of patient, and cycle characteristics. We review the clinical evidence on the effectiveness and safety of eFETs.


RESULTS
Randomized controlled trials (RCTs) comparing fresh and eFET yield contradictory results in terms of live birth rates. RCTs mainly involve women with an excessive response to ovarian stimulation. Studies including women with a normal or low ovarian response are either patient/physician preference or retrospective studies, prone to bias. Yet, they yield contradictory results as well. Overall, eFET seems to have limited potential to improve effectiveness of assisted reproductive technology, which could be limited to hyper-responders. Other suggested advantages of eFET include better obstetric and perinatal outcome. However, recent studies show that frozen embryo transfers can be associated with serious complications including hypertensive disorders during pregnancy, placenta accreta, or increased perinatal mortality.


CONCLUSIONS
The evidence behind advantages of eFET is of low quality. As such, switching to a universal eFET strategy does not seem justified. New RCTs including women from different strata of ovarian response are needed.
aDepartment of Obstetrics and Gynecology, Koc University School of Medicine, Istanbul, Turkey bDepartment of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Medicine, New Haven, Connecticut, USA.
Baris
B
Ata
Emre
E
Seli
D003362:Cost-Benefit Analysis; D015925:Cryopreservation; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011248:Pregnancy Complications / Q000517:prevention & control; D016032:Randomized Controlled Trials as Topic; D027724:Reproductive Techniques, Assisted