Freeze-all versus fresh blastocyst transfer strategy during in vitro fertilisation in women with regular menstrual cycles: multicentre randomised controlled trial [月经周期规律女性体外受精中冷冻与新鲜囊胚移植策略的比较：多中心随机对照试验]

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BMJ 2020; 370 doi: https://doi.org/10.1136/bmj.m2519 (Published 05 August 2020)
Cite this as: BMJ 2020;370:m2519

Authors
Sacha Stormlund, Negjyp Sopa, Anne Zedeler, Jeanette Bogstad, Lisbeth Prætorius, Henriette Svarre Nielsen, Margaretha Laczna Kitlinski, Sven O Skouby, Anne Lis Mikkelsen, Anne Lærke Spangmose, Janni Vikkelsø Jeppesen, Ali Khatibi, Nina la Cour Freiesleben, Søren Ziebe, Nikolaos P Polyzos, Christina Bergh, Peter Humaidan, Anders Nyboe Andersen, Kristine Løssl, Anja Pinborg

Abstract
Objective To compare the ongoing pregnancy rate between a freeze-all strategy and a fresh transfer strategy in assisted reproductive technology treatment.

Design Multicentre, randomised controlled superiority trial.

Setting Outpatient fertility clinics at eight public hospitals in Denmark, Sweden, and Spain.

Participants 460 women aged 18-39 years with regular menstrual cycles starting their first, second, or third treatment cycle of in vitro fertilisation or intracytoplasmic sperm injection.

Interventions Women were randomised at baseline on cycle day 2 or 3 to one of two treatment groups: the freeze-all group (elective freezing of all embryos) who received gonadotropin releasing hormone agonist triggering and single frozen-thawed blastocyst transfer in a subsequent modified natural cycle; or the fresh transfer group who received human chorionic gonadotropin triggering and single blastocyst transfer in the fresh cycle. Women in the fresh transfer group with more than 18 follicles larger than 11 mm on the day of triggering had elective freezing of all embryos and postponement of transfer as a safety measure.

Main outcome measures The primary outcome was the ongoing pregnancy rate defined as a detectable fetal heart beat after eight weeks of gestation. Secondary outcomes were live birth rate, positive human chorionic gonadotropin rate, time to pregnancy, and pregnancy related, obstetric, and neonatal complications. The primary analysis was performed according to the intention-to-treat principle.

Results Ongoing pregnancy rate did not differ significantly between the freeze-all and fresh transfer groups (27.8% (62/223) v 29.6% (68/230); risk ratio 0.98, 95% confidence interval 0.87 to 1.10, P=0.76). Additionally, no significant difference was found in the live birth rate (27.4% (61/223) for the freeze-all group and 28.7% (66/230) for the fresh transfer group; risk ratio 0.98, 95% confidence interval 0.87 to 1.10, P=0.83). No significant differences between groups were observed for positive human chorionic gonadotropin rate or pregnancy loss, and none of the women had severe ovarian hyperstimulation syndrome; only one hospital admission related to this condition occurred in the fresh transfer group. The risks of pregnancy related, obstetric, and neonatal complications did not differ between the two groups except for a higher mean birth weight after frozen blastocyst transfer and an increased risk of prematurity after fresh blastocyst transfer. Time to pregnancy was longer in the freeze-all group.

Conclusions In women with regular menstrual cycles, a freeze-all strategy with gonadotropin releasing hormone agonist triggering for final oocyte maturation did not result in higher ongoing pregnancy and live birth rates than a fresh transfer strategy. The findings warrant caution in the indiscriminate application of a freeze-all strategy when no apparent risk of ovarian hyperstimulation syndrome is present.

Trial registration Clinicaltrials.gov NCT02746562.