Interpretation:
Previous research has established that the success of IUI depends on various factors, including maternal age, sperm quality, type of subfertility, ovarian stimulation, and the timing of insemination18, 19.Given that spermatozoa and oocytes have only limited survival times, the appropriate timing of IUI relative to ovulation may be one of the most important factors influencing IUI success 6. Ovulation typically occurs 25-56 h following the onset of a spontaneous LH surge, whereas ovulation usually occurs 36-48 h after hCG administration in natural cycles.
Administration of hCG makes clinical prediction of ovulation more accurate; it permits planning for optimized time intervals between ovulation and insemination possible 20. This increased accuracy can likely help explain the significantly increased pregnancy rates achieved by the hCG group women in the present study. When insemination was performed twice, the window of sperm exposure to the oocyte was significantly increased; this maybe help explain the similar clinical pregnancy rates observed for the two groups21.
Several studies of ovarian hyperstimulation IUI cycles have demonstrated beneficial effects of hCG administration on IUI pregnancies22-24. One study by Taerk et al. (2017) reported that hCG administration significantly increased clinical pregnancy rates compared with monitoring of spontaneous serum LH surge in subfertile patients undergoing controlled ovarian hyperstimulation IUI cycles 22. Two additional retrospective studies of stimulated IUI have also reported that higher pregnancy rates resulted when hCG was given to trigger ovulation 23, 24.
Few studies have explored association(s) between hCG administration and pregnancy outcomes in natural cycle IUI. Moreover, the few studies addressing this topic have yielded inconsistent results. A Cochrane meta-analysis by Cantineau et al. (2014) reported no difference in pregnancy rates or live birth rates between natural cycle IUI patients timed according to spontaneous LH surge monitoring or hCG triggering 24. However, note that these reports included a total of only 264 women, and only one study reported live birth rate data.
To date, only one randomized clinical trial has investigated the pregnancy outcome of hCG administration for triggering ovulation in natural cycle IUI 9. A total of 300 patients were included in that study, of which 197 women used donor sperm. The trial concluded that administration of hCG resulted in decreased ongoing pregnancy rates. Given that the goal of IUI treatment is to achieve a healthy live birth, it is unfortunate that live birth rate data for the two groups was not reported from the trial.
A retrospective cohort study by El Hachem et al. (2017) found no difference in clinical pregnancy or live birth rates between urinary LH monitoring vs hCG-triggered ovulation in natural unstimulated therapeutic donor sperm insemination cycles 11. The inclusion criteria of that study were strict: only normo-ovulatory women were included. Notably, whereas the average age of the patients in that study was 32, the mean age of patients in our study was 27 years. We suspect that this 5 year age gap may be a major factor underlying the inconsistent conclusions of the two studies.