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

Objective
To compare perinatal outcomes between singleton live births following blastocyst-stage and cleavage-stage fresh embryo transfer using data from all United Kingdom (UK) licensed fertility clinics.

Design
Cohort study.

Setting
In vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycle-based data recorded in the UK Human Fertilisation and Embryology Authority (HFEA) anonymized dataset.

Patient(s)
60,926 IVF/ICSI cycles resulting in a singleton live birth after blastocyst-stage and cleavage-stage fresh embryo transfer between 2012 and 2018.

Intervention(s)
Baseline characteristics between IVF/ICSI blastocyst and cleavage-stage transfer groups were compared using the Chi-squared test for categorical/dichotomised variables and the Mann-Whitney test for continuous variables. Statistical significance was set at
Main Outcomes Measure(s)
Gestational age at birth and birth weight.

Result(s)
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 birth (PTB) (aRRR, 1.07; 95% CI, 1.00-1.15) and very preterm birth (VPTB) (aRRR, 1.05; 95% CI, 0.91-1.21) in singleton live births after fresh blastocyst and cleavage-stage transfer. Risk of low birth weight (LBW) (aRRR, 1.02; 95% CI, 0.95-1.09), very low birth weight (VLBW) (aRRR 0.96; 95% CI, 0.83-1.11), high birth weight (HBW) (aRRR, 0.97; 95% CI, 0.90-1.04) and very high birth weight (VHBW) (aRRR, 0.91; 95% CI, 0.77-1.08) were likely similar between the groups. Findings were consistent in the subgroup analysis.

Conclusion(s)
Fresh blastocyst transfer does not appear to have a negative impact on gestational age at birth and birth weight in singleton live births compared to fresh cleavage-stage transfer.