Perinatal outcomes in singleton live births after blastocyst transfer: an analysis of 60,926 in vitro fertilization cycles from the United Kingdom

Abstract

To compare perinatal outcomes between singleton live births after blastocyst-stage and cleavage-stage fresh embryo transfer using data from all United Kingdom licensed fertility clinics. A cohort study. Not applicable. A total of 60,926 in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles resulting in a singleton live birth after blastocyst-stage and cleavage-stage fresh embryo transfer between 2012 and2018. Baseline characteristics between IVF/ICSI blastocyst and cleavage-stage transfer groups were compared using the χ2 test for categorical/dichotomized variables and the Mann-Whitney test for continuous variables. Statistical significance was set at <.05. Association between perinatal outcomes and blastocyst transfer compared with cleavage-stage transfer was assessed using multinomial logistic regression, adjusting for confounders selected using directed acyclic graphs (95% confidence interval [CI], adjusted relative risk ratio [aRRR]). A subgroup analysis included cycles in women undergoing their first IVF/ICSI cycle. Gestational age at birth and birth weight. The blastocyst group comprised 42,677 IVF/ICSI cycles and cleavage-stage group 18,249 cycles. There was likely little to no difference in the risk of preterm (aRRR, 1.07; 95% CI, 1.00-1.15) and very preterm birth (aRRR, 1.05; 95% CI, 0.91-1.21) in singleton live births after fresh blastocyst and cleavage-stage transfer. Risks of low birth weight (aRRR, 1.02; 95% CI, 0.95-1.09), very low birth weight (aRRR 0.96; 95% CI, 0.83-1.11), high birth weight (aRRR, 0.97; 95% CI, 0.90-1.04), and very high birth weight (aRRR, 0.91; 95% CI, 0.77-1.08) were likely similar between the groups. The findings were consistent in the subgroup analysis. Fresh blastocyst transfer does not appear to have a negative impact on gestational age at birth and birth weight in singleton live births compared with fresh cleavage-stage transfer.