The aim of the study was to evaluate whether selecting embryos for transfer after prolonged culture after thaw (18-24 h) has better pregnancy rates than selecting embryos for transfer after short culture after thaw (2-5 h). We performed a double-blinded, randomized, controlled trial, evaluating 388 patients submitted to ART treatment who had embryos frozen on day-2 and subsequently transferred. All patients received the same endometrial priming with estradiol valerate followed by vaginal progesterone. Patients were randomized for Frozen embryo transfer 2-5 h after thaw (Group D2) or 18-24 h after thaw (Group D2/D3). The main Outcome Measure was ongoing pregnancy rate (OPR) at 20 weeks' gestation per embryo transfer. A total of 179 patients had embryos transferred 2-5 h after thaw and 209 patients had embryos transferred 18-24 h after thaw. The mean age in group D2 was 36 ± 4.4 and 36 ± 5.4 in group D2/D3. Ongoing pregnancy rate was 28% and 33.5% (p = 0.2) for groups D2 and D2/D3, respectively. These results suggest that increasing the culture time of embryos in one day to improve selection before transfer does not increase ongoing pregnancy rate. CLINICAL TRIAL REGISTRATION NUMBER: NCT03381001.

中文翻译：

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卵裂期胚胎解冻后不同的培养间隔（2 X 24 小时）是否会影响妊娠率？一项随机对照试验

该研究的目的是评估在解冻后长期培养（18-24 小时）后选择移植胚胎是否比解冻后短期培养（2-5 小时）后选择移植胚胎具有更高的妊娠率。我们进行了一项双盲、随机、对照试验，评估了 388 名接受 ART 治疗的患者，这些患者在第 2 天冷冻胚胎并随后转移。所有患者均接受相同的子宫内膜灌注，先是戊酸雌二醇，然后是阴道黄体酮。患者在解冻后 2-5 小时（D2 组）或解冻后 18-24 小时（D2/D3 组）随机接受冷冻胚胎移植。主要的结果指标是每次胚胎移植妊娠 20 周时的持续妊娠率 (OPR)。共有 179 名患者在解冻后 2-5 小时接受胚胎移植，209 名患者在解冻后 18-24 小时接受胚胎移植。D2 组的平均年龄为 36 ± 4.4，D2/D3 组为 36 ± 5.4。D2 组和 D2/D3 组的持续妊娠率分别为 28% 和 33.5%（p = 0.2）。这些结果表明，在一天内增加胚胎的培养时间以改善移植前的选择并不会增加持续妊娠率。临床试验注册号：NCT03381001。