Elective single embryo transfer strategy and clinical outcome analysis

Objective To evaluate the clinical value of elective single embryo transfer (eSET) on day 3. Methods A retrospective study was conducted on patients aged ≤38 years who received conventional in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) assisted reproduction treatment in the Department of Reproductive Medicine of Tianjin First Central Hospital from May 2014 to Mar 2019. According to the number of transferred embryos, they were divided into single embryo transfer group and double embryo transfer group; according to the embryo quality, they were divided into single high-quality embryo transfer group, double high-quality embryo transfer group and single high-quality embryo matching non-high-quality embryo transfer group (one excellent one non group); in addition, the single embryo and double embryo transfer groups were subdivided into cleavage embryo group and blastocyst group. The clinical pregnancy outcomes were compared among these groups. Results There was no statistically significant difference in the clinical pregnancy rate and the early abortion rate between the single embryo and double embryos transfer groups (P>0.05) in the fresh cycle. The implantation rate (36.22%) of the double embryo transfer group was lower than that of the single embryo transfer group (50.77%)（P=0.002）, while the multiple pregnancy rate (29.86%) was higher than that of the single embryo transfer group (0%) (P 0.05) in thawing cycles, while the multiple pregnancy rate in the double embryo transfer group (30.35%) was higher than that of the single embryo transfer group (2.50%) (P 0.05) in fresh and thawing cycles. The multiple pregnancy rate of single high-quality embryo group (0%) was significantly lower than that of double high-quality embryo group and a high-quality with a poor-quality embyo transfer group in fresh cycles (32.21%, 6.98%) (P 0.05) in thawing cycles. Conclusion The third day transplantation is more suitable for patients with 1 or 2 high-quality embryos, especially those with a high risk of multiple fetuses. eSET on the third day is a transplantation strategy that can better reduce the risk of multiple pregnancies. High-quality embryos are selected for transplantation or freezing, while non-high-quality embryos are further cultured and frozen according to the score for blastocyst formation. Thawed transplantation still has a good clinical pregnancy rate and has a high utilization value. Key words: Pregnancy rate; Elective single embryo transfer; Blastocyst culture; Implantation rate; Multiple pregnancy rate