Comparison of obstetric outcomes between single and double embryo transfers among singleton live births from vitrified donor oocyte IVF cycles: a cohort study.

Research Objective: Among singleton live births resulting from donor oocyte cycles, do perinatal outcomes differ between single (SET) and double embryo transfers (DET)?

Methods: We utilized a retrospective cohort of 610 recipients who had a singleton livebirth following nonidentified vitrified donor oocyte IVF cycle from a fertility clinic in the southeast US, 2008-2016. Perinatal outcomes included gestational age and birth weight. Preterm birth was defined as <37 weeks and low birth weight was defined as <2500 grams. Cluster weighted generalized estimating equations were used to calculate effect estimates adjusted for year, embryo stage, prior donor transfers, recipient and donor age, recipient and donor body mass index, and infertility diagnosis.

Results: Among the 698 singleton live births, 482 (69 %) were the result of a SET while 216 (31 %) were the result of a DET. Women who had two embryos transferred, as compared with one, did not have a statistically significant difference in gestational age (adjusted mean difference [AMD]:0.23 weeks, 95 % confidence interval [CI]:0.63, 0.17) or birth weight (AMD:27.9 grams, 95 % CI:137.7, 81.9). Similar, non-significant results were observed when evaluating risk of preterm birth and low birthweight.

Conclusion: We did not observe an adverse impact of DET on gestational age or birthweight compared to SET in singleton live births from donor cycles. While reassuring, clinicians should continue to use SET in donor oocyte recipients to reduce the adverse impact of multiple pregnancy and all the associated adverse birth outcomes.