The effect of endometrial thickness on live birth outcomes in women undergoing hormone-replaced frozen embryo transfer

Objective: To determine the impact of endometrial thickness on live birth outcomes and obstetric complication rate after hormone-replaced frozen embryo transfer. Design: Retrospective cohort study. Setting: Large, urban, academic fertility center. Patient(s): All patients with a singleton live birth after single euploid embryo transfer (by array comparative genomic hybridization or next-generation sequencing) in a hormone-replaced frozen embryo transfer cycle between January 2017 and December 2018 were reviewed. Intervention(s): None. Main Outcome measure(s): The primary outcomes were birth weight and obstetric complication rate. Result(s): A total of 492 patients were included. The median endometrial thickness was 8.60 mm (range, 6.0–20.0). The median gestational age at live birth was 39.4 weeks with a median birth weight of 3,345.2 g. Endometrial thickness was significantly correlated with birth weight. When patients were dichotomized into groups (those with an endometrial thickness of 7 mm), neonates born from endometria with a thickness of <7 mm were born earlier (37.3 vs. 39.4 weeks and born with lower birth weights (2,749.9 vs. 3,345.2 g). It should be noted that only seven patients had an endometrium measuring