Inspection depth of uterine lumen measured by transvaginal ultrasound is associated with the success of IVF: a prospective longitudinal cohort study in China

Objective To measure the inspection depth of uterine lumen by transvaginal ultrasound and assess the association between the inspection depth and pregnancy outcomes in IVF-ET. Methods This prospective longitudinal cohort study was conducted from June 2018 to December 2020. We enrolled patients aged 20-45 years who underwent frozen embryo transfer cycle. We calculated the average distance from the uterine lumen to the ultrasound probe (inspection depth) using transvaginal ultrasonography and divided the entire cohort into four groups according to the quartiles of the overall inspection depth distribution. The chi-square test was used to compare the pregnancy outcomes of the four groups. Univariate and multivariate regression analyses were performed to assess the association between the inspection depth and pregnancy outcomes. Results Seven hundred forty-two patients were finally enrolled, and they were grouped according to the inspection depth quartiles. There were significant decrease in the clinical pregnancy, implantation, and live birth rates among the four groups (P < 0.05); however, there was no significant difference in the miscarriage rate. Multivariable logistic regression analysis with the inspection depth as a continuous variable demonstrated that the inspection depth was associated with clinical pregnancy, implantation, and live birth rates (clinical pregnancy rate, adjusted odds ratio, 0.549; 95% confidence interval, 0.380-0.793; implantation rate, adjusted odds ratio, 0.680; 95% confidence interval, 0.496-0.931; live birth rate, adjusted odds ratio, 0.602; 95% confidence interval, 0.420-0.863), but not with the miscarriage rate. Conclusions The inspection depth of the uterine lumen measured by transvaginal ultrasound was associated with IVF success.