Predictive factors for intrauterine insemination outcomes: a review

PURPOSE: Intrauterine insemination (IUI) is a frequently utilized method of assisted reproduction for patients with mild male factor infertility, anovulation, endometriosis, and unexplained infertility. The purpose of this review is to discuss factors that affect IUI outcomes, including infertility diagnosis, semen parameters, and stimulation regimens. METHODS: We reviewed the published literature to evaluate how patient and cycle specific factors affect IUI outcomes, specifically clinical pregnancy rate, live birth rate, spontaneous abortion rate and multiple pregnancy rate. RESULTS: Most data support IUI for men with a total motile count > 5 million and post-wash sperm count > 1 million. High sperm DNA fragmentation does not consistently affect pregnancy rates in IUI cycles. Advancing maternal and paternal age negatively impact pregnancy rates. Paternal obesity contributes to infertility while elevated maternal BMI increases medication requirements without impacting pregnancy outcomes. For ovulation induction, letrozole and clomiphene citrate result in similar pregnancy outcomes and are recommended over gonadotropins given increased risk for multiple pregnancies with gonadotropins. Letrozole is preferred for obese women with polycystic ovary syndrome. IUI is most effective for women with ovulatory dysfunction and unexplained infertility, and least effective for women with tubal factor and stage III-IV endometriosis. Outcomes are similar when IUI is performed with ovulation trigger or spontaneous ovulatory surge, and ovulation may be monitored by urine or serum. Most pregnancies occur within the first four IUI cycles, after which in vitro fertilization should be considered. CONCLUSIONS: Providers recommending IUI for treatment of infertility should take into account all of these factors when evaluating patients and making treatment recommendations.