Effect of follicular size on clinical outcomes of frozen-thawed embryo transfer induced by hCG on ovulation in natural cycles / 中华妇产科杂志

ABSTRACT

Objective:To investigate the effect of follicular size on the clinical outcomes of frozen-thawed embryo transfer induced by human chorionic gonadotropin (hCG) of natural cycles on ovulation.Methods:Clinical data of 427 cycles of frozen-thawed single blastocyst transfer in Nanjing Drum Tower Hospital from January 2016 to December 2019 were retrospectively analyzed. The patients were divided into 15-16 mm group (15≤diameter≤16 mm, n=66), 16-17 mm group (16<diameter≤17 mm, n=101), 17-18 mm group (17<diameter≤18 mm, n=125), 18-20 mm group (18<diameter≤20 mm, n=109),>20 mm group (diameter>20 mm, n=26), according to the maximum follicle diameter on the induction day of hCG ovulation induction. The estradiol and luteinizing hormone (LH) levels, and clinical pregnancy rate, abortion rate and live birth rate were compared in five groups. Results:There were statistically significant differences in estradiol and LH levels among the five groups on the day of hCG induction (all P<0.05). Estradiol levels in 15-16 mm group to >20 mm group gradually increased on the day of hCG induction, and estradiol level in 15-16 mm group was significantly lower than those in 17-18 mm group, 18-20 mm group and >20 mm group (median 1 002.3 vs 1 103.3 vs 1 171.2 vs 1 539.0 pmol/L), with statistical significances ( P=0.034, P<0.001, P=0.002). On the day of hCG induction, LH levels in 15-16 mm group to >20 mm group showed a decreasing trend, and LH level in 15-16 mm group was significantly higher than those in 17-18 mm group and >20 mm group (median 37.73 vs 28.24 vs 24.11 U/L), with statistically significant differences ( P=0.007, P=0.006). There were no significant differences in clinical pregnancy rate, abortion rate and live birth rate in 15-16 mm group to >20 mm group (all P>0.05). Conclusion:In the natural cycle protocol of hCG induced ovulation, the small follicle group could achieve similar clinical outcomes compared with normal sized follicles in the single blastocyst transfer of frozen-thawed embryos.