The effect of endometrial thickness on the day of hCG administration on pregnancy outcome in the first fresh IVF/ICSI cycle

The aim of this study was to investigate the effect of endometrial thickness (EMT) on human chorionic gonadotropin (hCG) day on in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcome. A retrospective study was conducted on the clinical data of 756 patients in their first fresh IVF/ICSI cycle at the Wuxi Maternity and Child Health Hospital. Compared with the pregnancy failure group, the clinical pregnancy group had more transferable embryos and good-quality embryos and had a thicker endometrium (p < 0.05). The endometrial pattern was not significantly different between the two groups. EMT was found to be an independent prognostic factor for clinical pregnancy (adjusted OR = 1.25, 95% CI: 1.15-1.36, p < 0.01). Seven hundred and fifty-six cycles were categorized into three groups upon EMT on the hCG day: group 1 (EMT < 8 mm), 2 (EMT 8-14 mm) and 3 (EMT > 14 mm). Group1 had significantly lower clinical pregnancy, embryo implantation and live birth rates compared with group 2 and 3 (p < 0.01), while there was no significant difference in either spontaneous abortion or multiple-birth rate among these three groups. It was concluded that EMT on the hCG day was associated with pregnancy outcome in the first fresh IVF/ICSI cycle. A higher clinical pregnancy rate could be achieved when EMT ≥ 8 mm, and no adverse pregnancy outcome was observed when EMT > 14 mm.