P–402 Single embryo transfer in the Spanish public health system
Authors: Bueno. Rodriguez G , Rubio. Sanchez R , Moreno. de. Acevedo. Yagüe P 
Published: August 2021

Abstract

Study question
Are there significant advantages to transferring two embryos over transferring a single embryo in assisted reproduction?

Summary answer
The transfer of two embryos increases the number of miscarriages and multiple gestations without significantly increasing the pregnancy and live newborn rates.

What is known already
One of the most frequent complications in women who undergo in vitro fertilization treatments is multiple pregnancy. The objective of assisted reproductive techniques is to achieve a healthy and alive newborn. Therefore, for some years now, the embryo with the greatest implantation capacity to transfer has been chosen and, although the trend is to transfer a single embryo, the transfer rate of two embryos is still very high (60.3% according to the 2017 National Registry of the Spanish Fertility Society).

Study design, size, duration
Retrospective study in which 274 transfers made in the Assisted Reproduction Unit of the Valme University Hospital (Seville, Spain) during 19 months (November 2018 to May 2020) were analyzed. The transfers were divided into two groups: eSET (elective single embryo transfer) and DET (double embryo transfer).

Participants/materials, setting, methods
The rates of clinical pregnancy, multiple pregnancy, live newborn and abortion were evaluated in both groups. The comparison of the results was performed using Pearson’s Chi-square test (SPSS Statistics software). Statistical significance was defined as p &lt; 0.05.

Main results and the role of chance
Of the 274 embryo transfers performed, 195 were eSET (71.2%) and 79 DET (28.8%). The gestation rate in the eSET group was 43.1% while in the DET group it was 45.6%, with no statistically significant differences (p = 0.707). There was no multiple pregnancy in the eSET group while the multiple pregnancy rate in the DET group was 33.3%, with statistically significant differences (p &lt; 0.001). The abortion rate in the eSET group was 5.6% while in the DET group it was 13.9%, with statistically significant differences (p = 0.023). The live birth rate in the eSET group was 35.9% while in the DET group it was 31.6%, with no statistically significant differences (p = 0.504).
According to the results obtained in our Assisted Reproduction Unit, although the transfer of two embryos achieves a higher gestation rate, the difference is not statistically significant, so it should be reserved for very specific cases. The transfer of two embryos, on the other hand, increases the number of abortions (13.9%) and, above all, the number of multiple pregnancies (33.3%) that can lead to perinatal complications and mortality.

Limitations, reasons for caution
In this study the age of the patients and the cause of infertility were not taken into account. These two factors could influence the results obtained.
Wider implications of the findings: The results of this study support the elective transfer of a single embryo, as we are doing in our Assisted Reproduction Unit in 71.2% of cases, a figure much higher than the 37.2% of eSET nationwide

Trial registration number
Not applicable