Endometrial thickness is related to miscarriage rate, but not to the estradiol concentration, in cycles down-regulated with gonadotropin-releasing hormone antagonist

In this retrospective cohort study of 102 ovarian stimulation cycles for IVF/intracytoplasmic sperm injection using GnRH antagonist and gonadotropins, we sought to assess the effect of high E₂ levels on endometrial stripe thickness and its association with pregnancy outcomes and serum E₂ levels. We found no significant correlation between serum E₂ levels (both peak and area under the curve E₂ concentration) and the endometrial thickness. However, there was a statistically significant inverse relationship with early pregnancy loss (31%) if the endometrial thickness was <9.8 mm (sensitivity 71%; specificity 76%).