Effect of follicular diameter at the time of ovulation triggering on pregnancy outcomes during intrauterine insemination.

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.