Comparison of Pregnancy Outcomes of Letrozole-Induced Frozen-Thawed Embryo Transfer Cycles in PCOS women with two different abnormal ovulation patterns: A Retrospective Cohort Study

Objective The aim of this study was to compare whether pregnancy outcomes of the letrozole-induced endometrial preparation protocol in frozen-thawed embryo transfer (FET) cycles differed between oligo-ovulatory and anovulatory women with polycystic ovarian syndrome (PCOS).Materials and Methods In a retrospective study, women with PCOS who had undergone letrozole-induced FET at a university-affiliated fertility clinic from February 2014 to October 2020 were identified. The primary end point was live birth rate (LBR) per embryo transfer. Propensity score matching (PSM) and multivariate logistic regression analyses were performed to control for the relevant confounders.Results A total of 652 women with PCOS undergoing letrozole-induced FET were included in the final analysis. 363 of these women had oligo-ovulatory periods, while 289 had anovulatory periods. PSM analysis showed that LBR did not differ between groups (36.8% in oligo-ovulatory group vs. 32.8% in anovulatory group, P=0.431). Meanwhile, after PSM, the anovulatory group used extra gonadotrophin (Gn) for a longer duration (6.5±2.3 vs. 5.4±1.9, p=0.004, after PSM) and experienced a higher cycle cancellation rate (9.2% vs. 3.4%, p=0.028, after PSM) than the oligo-ovulatory group. Additionally, there were significantly lower crude odds of total pregnancy loss per positive pregnancy among oligo-ovulatory women than among anovulatory women (15.4% vs. 38.3%, p=0.001). Nevertheless, after controlling for potential confounding factors, LBR was significantly higher in anovulatory than oligo-ovulatory women [adjusted odds ratio (aOR) 1.57, 95% confidence interval (CI) 1.08 to 2.29, p=0.018]. Furthermore, the pregnancy loss rate (PLR) among the oligo-ovulatory group remained lower than those among the anovulatory group [aOR 0.23, 95%CI 0.12 to 0.44, p < 0.001].Conclusions PCOS women may experience different effects on pregnancy outcomes depending on their ovulation dysfunction patterns. Despite adjustment for confounding factors, those with oligo-ovulatory PCOS who underwent letrozole-induced FET had a higher LBR and lower PLR compared with those with anovulatory PCOS. This may indicate that when oligo-ovulation is detected, PCOS patients should be intervened in time to conceive as soon as possible. Prospective studies must be conducted in the future to verify our findings.