The effect of endometrial thickness on pregnancy rates in assisted reproductive technology (ART) patients has been evaluated by many authors, with controversial results. Endometrial thickness has been utilized as an indirect indicator for endometrial receptivity.

To evaluate relationship between endometrial thickness on day of embryo transfer and pregnancy outcome in in vitro fertilization and embryo transfer (IVF-ET) cycles. Should we cancel cycles based on endometrial thickness only?

A prospective analysis was conducted at Dr Kamini Rao Hospital, Bangaluru, of 239 patients. Various parameters were compared between pregnant and nonpregnant patients to see whether there is any cut-off for endometrial thickness on day of embryo transfer by which we can predict good prognosis in form of pregnancy and what effect other variables on endometrial thickness and pregnancy respectively and should we cancel embryo transfer, if endometrial thickness is not within certain range?

In the study population, 174 (73%) had primary and 65 (27%) had secondary infertility, Ovarian stimulation was performed with long protocol in 37% cases, antagonist protocol in 47% and other protocols like microflare, short, ultralong, ultrashort in 15%. Mean age of patients was 31.04 ± 3.79 years. Among causes of infertility male factor was present in 39%, tubal factor was seen in 18%, unexplained were 13%, polycystic ovarian syndrome in 11%, poor ovarian reserve in 4.1% and mixed causes in 13%. Majority of our patients were in normal and overweight as per body mass index (BMI). ET were easy in 90% of cases and 14 (5.8%) ETs were cancelled. The reason for cancellation was ovarian hyperstimulation syndrome (OHSS) in 9 cases, fluid in cavity in 2 cases, one patient had hyperpyrexia on day of ET and 2 cases of failed fertilization. Endometrial thickness was >10 mm in 35% cases. Overall clinical pregnancy rate was 39% with implantation rate of 21%, fertilization rate of 92% and cleavage rate of 95% and live birth rate of 26%. There were more follicles, oocytes and embryos, the endometrium was >10 mm and embryo quality was higher among women who became pregnant when compared with nonpregnant women after assisted reproduction though not statistically significant (p > 0.05). The pregnancy rate improved as endometrial thickness increased showing a linear association.

Increased endometrial thickness is associated with higher pregnancy rates, but as such a cut off cannot be decided. In our study we have seen pregnancies at both thin and thick endometrium so we should not cancel ET merely on the basis of endometrial thickness as pregnancy is affected by multiple variables and not by endometrial thickness alone.

Sharma R, Rao K, Srinivas MS, Jones T. Is Endometrial Thickness on the Day of ET Really Predictive of IVF Outcome? Int J Infertility Fetal Med 2012;3(2): 40-47.