. 2023 Jan 10;40(4):719–734. doi: 10.1007/s10815-022-02710-x

Table 1.

Basic characteristics of the included studies

Author, year, country	Study design	Period	Participants’ main characteristics	Sample size (pET/sET)	Age (pET/sET)	Embryo characteristics and endometrial preparation protocols	Outcomes
Bassil et al., 2018 Canada [46]	Single-center retrospective cohort	April 2016 to March 2017	pET group: patients who were < 42 years old, undergoing their first to third embryo transfer attempt; sET group: patients who underwent their first or second frozen embryo transfer at our clinic, < 42 years old; No patients with RIF in each group	53/503	(36.3 ± 0.40)^a / (35.6 ± 4.00)^a	Oocyte source: Unclear; Developmental stage: blastocyst (inferring from the endometrial preparation protocol); PGT for aneuploidy: 34.1% and 14.7% for the pET and sET groups, respectively; No. of embryos transferred: (1.1 ± 0.4) and (1.1 ± 0.3) for the pET and sET groups, respectively; Endometrial preparation protocol: programmed or modified natural protocols	OPR
Bergin et al., 2021 USA [9]	Single-center retrospective cohort	January 2014 to June 2019	Patients with different prior numbers of embryo transfers	After PSM: 133/353	After PSM: (36.25 ± 3.85)^a / (36.05 ± 3.81)^a	Oocyte source: autologous; Developmental stage: blastocyst (inferring from the endometrial preparation protocol); PGT for aneuploidy: 75.19% and 72.80% for the pET and sET groups, respectively; No. of embryos transferred: (1.09 ± 0.42) and (1.10 ± 0.30) for the pET and sET groups, respectively; Endometrial preparation protocol: natural or programmed protocols	CPR; LBR; MR; HCG positivity rate
Cozzolino et al., 2022 Spain [11]	Multicenter retrospective cohort	Unclear	Patients presenting with a previously failed embryo transfer	Autologous cycles: 255/1862; Donor cycles: 319/639	Autologous cycles: (36.79 ± 3.50)^a / (35.95 ± 3.82)^a; Donor cycles: (41.13 ± 4.19)^a / (42.16 ± 4.00)^a	Oocyte source: both autologous and donated; Developmental stage: both cleavage stage and blastocyst; PGT for aneuploidy: 31.9% and 36.5% for the pET and sET groups, respectively; No. of embryos transferred: ≥ 1; Endometrial preparation protocol: programmed protocol with GnRH downregulation	CPR; LBR; MR; OPR; HCG positivity rate; BPR
Doyle et al., 2022 USA [47]	Single-center retrospective cohort	2018 to 2019	Patients with different prior numbers of embryo transfers	307/2284	(36.70 ± 4.10)^a / (36.70 ± 4.30)^a	Oocyte source: autologous; Developmental stage: blastocyst; PGT for aneuploidy: all embryos transferred; No. of embryos transferred: 1; Endometrial preparation protocol: programmed protocol	CPR; LBR; HCG positivity rate
Fodina et al., 2021 Latvia [48]	Single-center retrospective cohort	2017 to 2020	RIF: patients who failed to achieve a clinical pregnancy after transfers of at least three good-quality embryos in different single fresh or frozen embryo transfers	PGT cycles: 72/87; Non-PGT cycles: 22/72	pET: (34.0 [38.0; 32.5])^b; pET + PGT: (35.0 [37.0; 33.0])^b; sET: (34.0 [37.0; 32.0])^b; sET + PGT: (36.0 [38.0; 34.0])^b	Oocyte source: unclear; Developmental stage: blastocyst; PGT for aneuploidy: 76.6% and 54.7% for the pET and sET groups, respectively; No. of embryos transferred: unclear; Endometrial preparation protocol: unclear	CPR; MR; HCG positivity rate; BPR
Jia et al., 2022 China [13]	Single-center retrospective cohort	November 2019 to March 2021	Patients with multiple embryo implantation failures (at least 2 cycles of embryo transfer, or transfer of at least 3 good-quality blastocysts with a Gardner’s score of 4BB or higher)	140/141	(32.01 ± 2.99)^a / (31.87 ± 3.21)^a	Oocyte source: unclear; Developmental stage: blastocyst; PGT for aneuploidy: unclear; No. of embryos transferred: ≥ 1; Endometrial preparation protocol: unclear	CPR; MR; IR; HCG positivity rate; BPR
Neves et al., 2019 Spain [49]	Single-center retrospective cohort	October 2012 to December 2018	Patients who had undergone one of the following: (a) ≥ 1 previous failed euploid embryo transfer (Euploid-ET) and (b) ≥ 2 previous failed ET from reception cycles (Donor-ET) without PGT-A	24/119	(39.25 ± 3.99)^a / (39.18 ± 3.80)^a	Oocyte source: both autologous and donated; Developmental stage: blastocyst; PGT for aneuploidy: all autologous embryos; No. of embryos transferred: ≥ 1; Endometrial preparation protocol: programmed protocol	CPR; IR
Ohara et al., 2022 Japan [50]	Two-center retrospective cohort	April 2019 to June 2020	RIF: patients who failed to achieve clinical pregnancy with three or more IVF cycles in which one or two morphologically good-quality blastocysts were transferred	After PSM: 215/215	After PSM: (38.50 ± 4.10)^a / (38.20 ± 4.30)^a	Oocyte source: autologous; Developmental stage: blastocyst; PGT for aneuploidy: none; No. of embryos transferred: (1.39 ± 0.5) and (1.41 ± 0.5) for the pET and sET groups, respectively; Endometrial preparation protocol: programmed protocol	CPR; MR; LBR
Riestenberg et al., 2021 USA [10]	Single-center prospective not randomized cohort	January 2018 to April 2019	Patients who had their first single euploid FET in a programmed cycle	147/81	(36.90 ± 3.80)^a / (34.90 ± 3.80)^a	Oocyte source: autologous; Developmental stage: blastocyst; PGT for aneuploidy: all embryos transferred; No. of embryos transferred: 1; Endometrial preparation protocol: programmed protocol	CPR; LBR; MR; HCG positivity rate; BPR
Simón et al., 2020 Spain [12]	Multicentre RCT	November 2013 to April 2017	Patients without recurrent miscarriage (more than two previous biochemical pregnancies or spontaneous abortions); implantation failure (more than three failed IVF cycles with good-quality embryos transferred)	Per-protocol analysis set: 80/92	(33.00 ± 3.10)^a / (32.80 ± 3.40)^a	Oocyte source: per-protocol analysis set: autologous; Developmental stage: both cleavage stage and blastocyst; PGT for aneuploidy: 4.3% and 2.7% for the pET and sET groups, respectively; No. of embryos transferred: ≥ 1; Endometrial preparation protocol: programmed protocol	IR; LBR; MR; HCG positivity rate; BPR

pET, personalized embryo transfer; sET, standard embryo transfer; No., number; FET, frozen-thawed embryo transfer; RIF, recurrent implantation failure; PGT, preimplantation genetic testing; CPR, clinical pregnancy rate; LBR, live birth rate; HCG, human chorionic gonadotropin; BPR, biochemical pregnancy rate; MR, miscarriage rate; IR, implantation rate; OPR, ongoing pregnancy rate; PSM, propensity score matching; RCT, randomized controlled trial; GnRH, gonadotropin-releasing hormone

^aAges shown as mean age ± (standard deviation)

^bAges shown as median age (interquartile range)