Evaluating the role of endometrial thickness on hcg ınjection day: a predictive marker for reproductive success in clomiphene-IUI cycles

ABSTRACT
Introduction. Endometrial thickness (EMT) on the day of hCG administration is critical for predicting reproductive success in intrauterine insemination (IUI) cycles with clomiphene citrate (CC). However, the optimal EMT for clinical pregnancy and live birth outcomes remains unclear. In this study, the influence of EMT on reproductive outcomes in CC+IUI cycles is investigated.
Materials and Methods. This retrospective analysis included 640 IUI cycles performed at a tertiary reproductive endocrinology center between February 2019 and February 2020. Participants were couples with unexplained infertility or WHO category 2 anovulation. All underwent ovulation induction with CC, and EMT was measured via transvaginal ultrasound on the day of the hCG trigger. Outcomes included clinical pregnancy and live birth rate.
Results. Of 640 cycles, 80 (12.5%) achieved clinical pregnancy, with 52 (8.1%) resulting in live births. Spontaneous abortion occurred in 23 cases (3.6%). Age, duration of infertility and CC dose had a significant impact on clinical pregnancy and live birth rates. The optimal EMT threshold for predicting clinical pregnancy was 8.45 mm (sensitivity 49.4%, specificity 55.3%). An EMT between 8–9 mm was associated with higher clinical pregnancy (p=0.010) and live birth rates (p=0.002).
Conclusions. EMT has a significant impact on pregnancy outcome in CC+IUI cycles, with 8–9 mm being the optimal range for better outcomes. However, EMT alone shows moderate predictive accuracy and should be combined with other clinical factors in decision making. Further research is needed to refine prediction models that integrate EMT, patient age and duration of infertility to improve outcomes.