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.