Association between Myometrial Thickness and Assisted Reproductive Technologies Outcomes: A Prospective Cohort Study.

Background: Myometrial thickness has been expected to be a prognosticator for lower uterine segment function. An abnormal function of the uterine muscle layer can cause common and important reproductive problems. This study aimed to evaluate the relationship between baseline myometrial thickness and assisted reproductive technologies (ART) outcomes.

Materials and methods: In this prospective cohort study, 453 infertile women undergoing ART cycles without any obvious uterine pathology, participated in this prospective cohort study from February 2013 to May 2015. In order to measure the myometrial thickness in the anterior and posterior of the uterine, trans-vaginal ultrasounds were conducted on days 2-4 of the cycle (menstrual phase) preceding ovarian stimulation and the day of human chorionic gonadotropin (hCG) injection. We defined three groups based on the baseline myometrial thickness in the anterior and posterior, including (A) <25 mm, (B) 25-29.9 mm and (C) ≥30 mm. Ovarian stimulation, oocyte retrieval and luteal phase support were performed in accordance with the standard long protocol. Two weeks after embryo transfer, the patients underwent a pregnancy test by checking their serum β-hCG levels. The primary outcome measure was clinical pregnancy rate. Secondary outcome measures were, implantation rate, abortion rate and live birth rate.

Results: The clinical pregnancy (P=0.013) and implantation (P=0.003) rates were significantly lower in group A than in two other groups. Although the live birth rate was lower in group A than two other groups, this decrease was not statistically significant (P=0.058).

Conclusion: The findings may be a way for clinicians to draw focus on providing therapeutic strategies and a specific supportive care for women with a baseline myometrial thickness <25 mm in order to improve the reproductive outcome of in vitro fertilization/intracytoplasmic sperm injection (IVF-ICSI).