Objective: To compare pregnancy outcomes when triggering ovulation at different follicle sizes during intrauterine insemination (IUI) cycles.
Methods: A prospective observational study was undertaken at two collaborative fertility centers in Saudi Arabia between January 2014 and May 2016. Women of any age were enrolled if they met inclusion criteria: primary, secondary, or unexplained infertility (≥1 year); day-2 follicle-stimulating hormone less than 12 IU/mL; normal prolactin, thyroid function, and uterine cavity; at least one patent tube; and a male partner with normal semen count and motility. IUI cycles were subdivided by size of dominant follicle (17 to <18 mm, 18 to <19 mm, 19 to <20 mm, and ≥20 mm), and pregnancy outcomes compared.
Results: Data from 516 IUI cycles were analyzed. Frequencies of clinical pregnancy, ongoing pregnancy, and live birth for a follicle size of 19-20 mm were 30.2% (39/129), 24.0% (31/129), and 24.0% (31/129), respectively; these rates were significantly higher than those in other groups (all P<0.05). Only endometrial thickness was found to also contribute to outcome: probability of pregnancy increased as thickness rose (odds ratio 1.148, 95% confidence interval 1.065-1.237; P<0.001).
Conclusion: The optimal follicular diameter associated with increased pregnancy rates in gonadotropin-stimulated IUI cycles was between 19 and 20 mm.
Keywords: Endometrial thickness; Follicle size; Gonadotropin stimulation; Intrauterine insemination; Ovulation induction; Pregnancy outcomes.
© 2017 International Federation of Gynecology and Obstetrics.