THE ASSOCIATION BETWEEN OVULATORY SURGE TYPE AND PREGNANCY OUTCOME AMONG PATIENTS UNDERGOING INTRAUTERINE INSEMINATION.

To determine whether ovulatory surge type (human chorionic gonadotropin (hCG) ovulatory trigger, endogenous luteinizing hormone (LH) surge, or a combination of both) is associated with pregnancy rate in clomiphene citrate, letrozole, or natural intrauterine insemination (IUI) cycles. We conducted a retrospective cohort study of infertile women who underwent IUI at a single academic center from 01/2015 to 12/2019. We included women ≤42 years old undergoing their first IUI in a natural cycle or after ovulation induction with clomiphene citrate or letrozole. We excluded women with an LH of ≥17 IU/L at cycle start and patients with severe male factor (defined as post-wash total motile sperm count of ≤5x106). An endogenous surge was defined as LH of ≥17 IU/L. For patients without an endogenous LH surge, either purified or recombinant hCG was administered. The primary outcome was clinical pregnancy. A modified Poisson regression with robust error variance adjusted a priori for age and number of follicles ≥14 mm at the time of trigger or LH surge was performed to estimate the relative risk with a 95% confidence interval (CI) for outcomes. Further variables were retained in the regression model if their addition to the base model changed the RR from the crude model by 10% or more. Covariates tested include BMI, interval between surge and IUI, and peak endometrial stripe thickness. These covariates did not meet criteria to be included in the model. A subgroup analysis was performed to assess pregnancy rate by ovulatory surge type among each cycle type, which was analyzed with a Fisher’s exact test due to a frequency of <5 in some of the subgroup categories. A total of 2,606 patients were included. Among all cycles, the clinical pregnancy rate was 13.7%. Compared to the endogenous LH surge group, the clinical pregnancy rate was similar among the ovulatory trigger alone group (1.06 [CI 0.79-1.45]) and the combination LH surge with ovulatory trigger group (0.82 [CI 0.43-1.58]). Similarly, in the subgroup analysis, there were no differences in the clinical pregnancy rates across the three ovulatory surge types for clomiphene citrate/IUI (p=0.645), letrozole/IUI (p=0.118), and natural cycle/IUI (p=1.00). There is no difference in the clinical pregnancy rate among all cycles regardless of which ovulatory surge type was used to time IUI. Additionally, within clomiphene citrate/IUI, letrozole/IUI, or natural/IUI cycles, there was no benefit to one ovulatory surge type over the other.