Follicle number and size as predictors of pregnancy outcome in unexplained infertility couples treated with clomiphene citrate and intrauterine insemination

Abstract

Ovulation induction with intrauterine insemination (IUI) increases pregnancy rates in couples with unexplained infertility. However, the optimal number or size of follicles required to achieve pregnancies and live births is unknown. Our objective was to evaluate whether the number and/or size of mature follicles in patients with unexplained infertility treated with Clomiphene Citrate (CC) and intrauterine insemination are predictors of pregnancy and live birth rates. Retrospective cohort study from two academic institutions. 414 treatment cycles of couples from the infertility clinics at UT Medicine San Antonio, Texas and the Cleveland Clinic, Cleveland, Ohio were included. All couples were diagnosed with unexplained infertility and were treated with CC and IUI between 2005-2012. Primary outcomes were pregnancy rate and live birth rate and analyzed by the number and size of mature follicles. The secondary outcome analyzed was the multiple pregnancy rate. Statistical analysis using Chi Square, T tests and logistic regression was performed as appropriate. P < 0.05 was considered statistically significant. Pregnancy rates significantly increased in women with two dominant follicles (defined as >16 mm). Similarly, there was a higher live birth rate in patients found to have two or three mature follicles in comparison to a single follicle, P<0.05. In addition, pregnancy rates significantly increased when the size of the mature follicle was ≥ 18-20 mm (OR = 1.92, 95% CI [1.35, 2.72]; P = 0.0003) and > 20mm (OR 1.56, 95% CI [1.12, 2.18], P = 0.0084). The probability of a live birth also increased when the size of the mature follicle was ≥ 18-20 mm (OR = 1.90, 95% CI [1.28, 2.81; P = 0.0014) and > 20mm (OR 1.86, 95% CI [1.28, 2.72], P = 0.0012.) A higher rate of multiple gestations was found with three or more mature follicles but this was not statistically significant. Higher pregnancy and live birth rates are achieved in patients with unexplained infertility treated with CC and IUI when patients have at least two mature follicles with size ≥18 mm. A prospective randomized trial is needed to confirm our findings.