[The effect of unexpected follicular development in artificial cycles on the clinical outcomes in frozen thawed embryo transfer based on propensity score matching].

To study the effect of unexpected follicular development in artificial cycles on the clinical outcomes in frozen thawed embryo transfer based on propensity score matching(PSM). The retrospective cohort study analyzed the clinical data of 7 064 cycles (5 716 patients) of artificial cycle frozen-thawed embryo transfer (AC-FET) in the Reproduction Center of the Third Affiliated Hospital of Zhengzhou University from January 1, 2016 to December 31, 2020. The clinical data were divided into three groups according to the degree of follicular development in AC-FET: no follicular growth group (group A, 6 349 cycles), small follicular growth group (group B, 248 cycles), and large follicular growth group (group C, 467 cycles). Differences in clinical outcomes between the small follicle growth group (Group B) and the large follicle growth group (Group C) were compared with the no follicle growth group (Group A) after PSM and logistic regression to adjust for confounding factors at baseline. A binary logistic regression model was used to analyze the factors related to the unanticipated follicular development in AC-FET. Age [(,)] was [31.0 (28.0, 36.0)] years in Group A, [34.5 (30.0, 40.0)] years in Group B, and [36.0 (31.0, 41.0)] years in Group C. After adjusting for confounders, the differences between Groups A and B in clinical pregnancy rate (=0.169), live birth rate (=0.318), early abortion rate (=0.470), and miscarriage rate (=0.783) were not statistically significant. The differences in clinical pregnancy rate (=0.743), live birth rate (=0.486) and miscarriage rate (=0.080) between Groups A and C were not statistically significant, while early miscarriage rate (=0.034) differences were statistically significant. The age, BMI, basal AFC, AMH and starting dose of estrogen were correlates of the emergence of non-expected small follicles in Groups B and A. The adjusted () values (95%) were 1.03 (1.01-1.06), 0.93 (0.90-0.98), 0.97 (0.95-0.99), 0.96 (0.95-0.97), and 0.59 (0.45-0.77), all <0.05. Age, basal AFC, AMH and starting dose of estrogen were the associated factors of the appearance of non-expected large follicles in Groups C and A. The values (95%) were 1.03 (1.01-1.05), 0.93 (0.91-0.95), 0.96 (0.95-0.97), and 0.52 (0.42-0.64), all <0.05. In AC-FET, the clinical outcome of small follicular growth is similar to that of unfollicular growth; Compared with the growth without follicles, the growth and development of large follicles can reduce the early abortion rate; Patients with older age, less AFC, lower AMH, and lower initial dose of estrogen could be more likely to have unanticipated follicular development during endometrial preparation.