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 E(2) levels on endometrial stripe thickness and its association with pregnancy outcomes and serum E(2) levels. We found no significant correlation between serum E(2) levels (both peak and area under the curve E(2) 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%).