Ongoing pregnancy rate is associated with trigger-day progesterone level in letrozole/clomiphene intrauterine insemination cycles.

PURPOSE: Prior studies in fresh embryo transfer IVF cycles have associated elevated serum progesterone level on day of ovulatory trigger, particularly if ≥ 1.5 ng/ml, with decreased pregnancy rates. A similar association has been found in intrauterine insemination (IUI) cycles using gonadotropins for ovulation induction. The purpose of this study was to evaluate the association of trigger-day progesterone level with pregnancy rates in IUI cycles using oral ovulation induction agents.

METHODS

A retrospective cohort study was conducted at a multicenter private practice. 4,866 IUI cycles using letrozole or clomiphene were analyzed from January 1, 2017, to December 31, 2023. The primary outcome measure was ongoing pregnancy per cycle as a function of the serum progesterone level obtained on the day of ovulatory trigger. Secondary outcome measures were positive pregnancy, clinical pregnancy, and pregnancy loss.

RESULTS

When compared to cycles with trigger-day progesterone < 1 ng/ml, ongoing pregnancy was significantly lower when progesterone was ≥ 1.5 ng/ml (11.9% versus 5.6%; Risk Ratio (RR) 0.46 (95% CI 0.25-0.84)). Ongoing pregnancy was comparable when progesterone was < 1 ng/ml or 1-1.49 ng/ml (11.9% versus 9.2%; (RR 0.75 (95% CI 0.55-1.03)). Positive pregnancy and clinical intrauterine pregnancy outcomes were also significantly lower in the ≥ 1.5 ng/ml versus < 1 ng/ml group, but comparable in the < 1 ng/ml and 1-1.49 ng/ml groups. Pregnancy loss was not significantly different between groups.

CONCLUSION

Pregnancy outcomes are optimized when trigger-day progesterone level is < 1.5 ng/ml in IUI cycles using oral ovulation induction agents, highlighting the value of obtaining a progesterone level on the day of ovulatory trigger.