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

No studies have been conducted on the impact of different types of ovulatory dysfunction on the outcomes of frozen-thawed embryo transfers (FETs) in a letrozole-stimulated cycle in women with polycystic ovarian syndrome (PCOS). This study aimed to compare whether pregnancy outcomes of the letrozole-induced protocol in FET cycles differed between oligo-ovulatory and anovulatory women with PCOS. In a retrospective cohort 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 and multivariate logistic regression analyses were performed to control for the relevant confounders. A total of 652 women with PCOS undergoing letrozole-induced FET were included in the final analysis. Three hundred sixty-three of these women had oligo-ovulatory periods, while 289 had anovulatory periods. Propensity score matching analysis showed that LBR did not differ between groups (36.8% in oligo-ovulatory group vs 32.8% in anovulatory group, P = .431). Nevertheless, after controlling for potential confounding factors, LBR was significantly lower in anovulatory than oligo-ovulatory women (adjusted odds ratio 1.57, 95% confidence interval 1.08-2.29, P = .018). Furthermore, the pregnancy loss rate among the oligo-ovulatory group remained lower than those among the anovulatory group (adjusted odds ratio 0.23, 95% confidence interval 0.12-0.44, P < .001). Despite adjustment for confounding factors, those with oligo-ovulatory PCOS had a higher LBR and lower pregnancy loss rate 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.