An updated Cochrane review of 42 randomized controlled trials involving 6603 subfertile couples evaluated how different ovulation-timing methods affect live birth and clinical pregnancy outcomes in IUI cycles. The findings show that varying the timing interval between hCG trigger and insemination—from under 33 hours to over 40 hours—produced highly imprecise results, offering no reliable evidence to support one timing strategy over another. Comparisons between hCG triggering, LH surge–based timing, and different hCG formulations similarly showed no clear differences in live birth or ongoing pregnancy outcomes.
The review also found low-certainty evidence suggesting that combining hCG with FSH may modestly improve pregnancy outcomes compared with hCG alone, though results came from a single study. Across all comparisons, clinical pregnancy rates, miscarriage, multiple pregnancy, and ectopic pregnancy outcomes showed no meaningful differences, and overall evidence was limited by small sample sizes and serious imprecision. The authors conclude that current research does not identify a superior method for synchronizing ovulation and insemination, emphasizing the need for larger, high-quality trials to clarify best practices.
Keywords: intrauterine insemination, ovulation triggering, hCG timing, fertility outcomes