Liu KE, et al. - In this retrospective cohort analysis, experts studied the effect of endometrial thickness on pregnancy and live birth rates in fresh and frozen in vitro fertilization (IVF) cycles. For this investigation, 33 Canadians clinics partook in voluntary reporting of IVF and pregnancy outcomes to the CARTR-BORN database. The study findings suggested that clinical pregnancy and live birth rates decline as the endometrial thickness decreases below 8 mm in fresh IVF-embryo transfer (ET) and below 7 mm in frozen–thaw ET cycles. When confronted with decisions related to a persistently thin endometrium, these data provide valuable guidance for both practitioners and patients.