A randomized trial comparing time intervals from HCG trigger to intrauterine insemination for cycles utilizing GnRH antagonists

Intrauterine insemination (IUI) during ovarian stimulation cycles is typically performed 36 hours after human chorionic gonadotropin (hCG) injection. We hypothesized that adjusting the time interval to IUI to better coincide with ovulation may increase pregnancy rates. Patients undergoing induction of ovulation utilizing gonadotropins and gonadotropin releasing hormone (GnRH) antagonists and IUI were divided to three groups based on the time from hCG injection to IUI: 36, 42, and 48 hours. Primary outcome was defined as the clinical pregnancy rate. Secondary outcomes comprised additional parameters including multifetal pregnancy rate. A total of 92 patients completed the study. Baseline parameters were similar between the groups. The clinical pregnancy rate in the three groups was 20%, 38%, and 24%, respectively. While the 42 hour time interval had a higher numerical pregnancy rate, the pregnancy rates did not differ statistically among the study groups. The multifetal pregnancy rate did not differ among the three groups as well. A larger study is necessary to ascertain if a 42 hour time interval can indeed improve pregnancy rates.