Single-embryo transfer results in favourable postnatal outcomes compared to double-embryo transfer

A new study published in the Journal of American Medical Association found that the chances of unfavorable outcomes following double-embryo transfer (DET) was higher compared to singletons born after single-embryo transfer (SET), even when the outcome is a singleton birth. 

Compared to pregnancies after normal conception, pregnancies originating from assisted reproductive technology carry a higher risk of poor postnatal outcomes. Previous research has linked several embryo transfers that resulted in pregnancies to these unfavorable results. Thus, this study was carried out by Kenny A. Rodriguez-Wallberg and colleagues compare the risk of unfavorable outcomes in singletons born by assisted reproduction utilizing double-embryo transfer and single-embryo transfer.

Data from women who delivered a singleton following SET or DET in Sweden between 2007 and 2017 were utilized in this cohort research. These women's data were kept in the National Quality Registry for Assisted Reproduction. We included all embryo transfers, whether they replaced cleaved or blastocyst-stage embryos in fresh or frozen treatment cycles. Linking to the National Medical Birth Register enabled the retrieval of information on obstetric and neonatal outcomes. As a reference group, naturally developed singletons were used. Between September 2021 and August 2022, data were examined. For obstetric and perinatal outcomes in singleton babies conceived with DET vs. SET, relative risk ratios or odds ratios (ORs) and absolute risk differences (ARDs) were estimated in percentage points with 95% confidence intervals.

The key findings of this study were:

30 713 singletons and 5123 singletons were born among the 1 115 863 births of singletons, respectively. 

After DET vs. SET, singletons had a greater risk of neonatal mortality. 

DET was linked to a greater risk of low birth weight in frozen embryo transfers. 

DET was linked to extremely preterm delivery and poor birth weight among blastocyst transplants.

In conclusion, the findings are in favor of using SET; however, women who are older or who otherwise have low reproductive potential should not be discouraged from using DET due to the higher risk that was observed after DET.

Reference: 

Rodriguez-Wallberg, K. A., Palomares, A. R., Nilsson, H. P., Oberg, A. S., & Lundberg, F. (2022). Obstetric and Perinatal Outcomes of Singleton Births Following Single- vs Double-Embryo Transfer in Sweden. In JAMA Pediatrics. American Medical Association (AMA). https://doi.org/10.1001/jamapediatrics.2022.4787