P-212 Balancing success and safety in assisted reproductive technologies cycles: the outcomes of transferring poor-quality blastocyst or day 5 slow-growing embryos with good-quality blastocyst
Authors: Polumiskova A 
Published: July 2024

Abstract

Study question
Does transferring two mixed-quality embryos improve the live birth rate (LBR) without increasing the multiple gestation rate compared to the single good-quality blastocyst (GQB) transfers?

Summary answer
The transfers of single GQB and two mixed-quality embryos show similar LBRs, however, the multiple gestation rate was significantly higher in double embryo transfer groups.

What is known already
Due to higher LBR after blastocyst transfer, the single embryo transfer (SET) strategy has gained popularity worldwide. Despite that double-embryos transfers (DET) demonstrate higher LBR than SET, multiple gestation rates (MGRs) are higher in DET. To reduce MGR but still accomplish high LBR, DETs could be performed using embryos of mixed-quality. It has been suggested that the transfer of GQB with poor-quality blastocyst (PQB) could increase LBR without increasing MGR. Alternatively, when the embryo transfer is scheduled in a fresh cycle, the DET could be performed with GQB and day 5 slow-growing embryo (SGE) – early blastocyst or morula.

Study design, size, duration
This study included assisted reproductive technologies (ART) cycles with fresh embryo transfer on day 5, between 2015 and 2021, for patients under 34 years. Selected ART cycles were assigned into five groups: SET with GQB (SET-GQB, n = 754); DET with two GQBs (DET-GQB, n = 306); DET with one GQB and one PQB (DET-GP, n = 75); DET with one GQB and one day 5 SGE (DET-GS, n = 386), DET with two day 5 SGE (DET-SGE, n = 209).

Participants/materials, setting, methods
According to Gardner and Schoolcraft’s grading system, blastocyst morphological assessment was performed on day 5. Blastocysts graded as AA, AB, BA, and BB with a degree of expansion ≥3 were classified as GQBs, whereas blastocysts graded ВС, СВ, СС with a degree of expansion ≥3 were classified as PQBs. Day 5 morulas and blastocysts with degree of expansion 1 were classified as slow-growing embryos. The cycles with donor gametes, preimplantation genetic testing were excluded.

Main results and the role of chance
The LBR was significantly higher in DET-GQB than in SET-GQB [53,59% (164/306) vs 40,58% (306/754); P &lt; 0,001]. There were no significant differences in implantation rate (IR) and miscarriage rate (MR) between SET-GQB and DET-GQB [47,88% (361/754) vs. 44,12% (270/612) P = 0,165], [12,19% (44/361) vs. 10,00% (27/270) P = 0,389]. However, the MGR was significantly higher in DET-GQB compared to SET-GQB [36,59% (60/164) vs 1,31% (4/306) P &lt; 0,001].
When SET-GQB was compared with DET-GS, DET-GP there were no significant differences in LBR: [40,58% (306/754) vs. 39,64% (153/386) P = 0,757; vs. 41,33% (31/75) P = 0,899]. The IR was significantly higher in SET-GQB than in DET-GS and DET-GP [47,88% (361/754) vs. 30,70% (237/772) P &lt; 0,001; vs. 30,00% (45/150) P &lt; 0,001]. There were no significant differences in MR between SET-GQB and DET-GS, DET-GP [12,19% (44/361) vs. 17,30% (41/237) P = 0,079; vs. 11,11% (5/45) P = 0,834]. However, the MGR was significantly lower in SET-GQB compared to DET-GS, DET-GP [1,31% (4/306) vs. 18,95% (29/153) P &lt; 0,001; vs. 22,58% (7/31) P &lt; 0,001].
The IR and LBR were significantly higher in SET-GQB compared to DET-SGE [47,88% (361/754) vs 16,99% (71/418) P &lt; 0,001], [40,58% (306/754)vs 19,14% (40/209) P &lt; 0,001]. The MR and MGR were significantly lower in SET-GQB than in DET-SGE [12,19% (44/361) vs 32,39% (23/71) P &lt; 0,001], [1,31% (4/306) vs 15,00% (6/40) P &lt; 0,001].

Limitations, reasons for caution
The study is limited due to the uneven distribution and a low number of participants in group DET-GP. Blastocyst morphological assessment remains subjected to a human factor. It was impossible to form a group where two PQBs were transferred, as there were only a few cases of such transfers.

Wider implications of the findings
Transferring an additional poor-quality embryo (poor-quality blastocyst or day 5 slow-growing embryo) does not increase the live birth rates. However, it significantly raises the multiple gestation rate. Despite the low live birth rate when two day 5 slow-growing embryos are transferred, the multiple gestation rate significantly increases, compared to SET.

Trial registration number
Not applicable