Comparison of perinatal outcomes of expected high ovarian response patients and normal ovarian response patients based on antral follicles undergoing frozen-thawed embryo transfer in natural cycle/small amount of HMG induced ovulation cycle
Authors: Zhang Wenjuan , Liu Zhaozhao , Wang Bijun , Liu Manman , Li Jiaheng , Guan Yichun 
Published: September 2023

Background
Due to the high risk of complications in fresh cycle transfer among expected high ovarian response patients, most choose frozen-thawed embryo transfer (FET). There is currently few researches on whether the FET outcomes of expected high ovarian response patients with regular menstrual cycles are similar to those of normal ovarian response. Therefore, our objective is to explore and compare pregnancy outcomes and maternal and neonatal outcomes of natural FET cycles between patients with expected high ovarian response and normal ovarian response with regular menstrual cycles based on the antral follicle count (AFC).
Methods
This retrospective cohort study included 5082 women undergoing natural-cycle FET in the Reproductive Center of the Third Affiliated Hospital of Zhengzhou University from January 1, 2017, to March 31, 2021. The population was divided into expected high ovarian response group and normal ovarian response group based on the AFC, and the differences in patient characteristics, clinical outcomes and perinatal outcomes between the two groups were compared.
Result
Regarding patient characteristics, compared with the normal ovarian response group, the expected high ovarian response group was younger (30.68 ± 3.80 vs. 32.55 ± 3.91 y), had a higher proportion of women with primary infertility (42.22% vs. 37.30%), a shorter duration of infertility (3.07 ± 2.39 vs. 3.48 ± 2.98 y), a higher anti-Müllerian hormone (AMH) level (31.17 ± 23.45 vs. 14.45 ± 10.86), a higher proportion of human menopausal gonadotrophin (HMG)-induced cycles (17.68% vs. 13.91%), a thicker endometrium on the day of embryo transfer (9.74 ± 1.67 vs. 9.60 ± 1.64), and a higher proportion women undergoing single embryo transfer (59.56% vs. 51.28%). Regarding clinical outcomes, compared with the normal ovarian response group, the expected high ovarian response group had a higher clinical pregnancy rate (57.34% vs. 48.50%) and live birth rate (48.12% vs. 38.97%). There was no difference in the early miscarriage rate and twin pregnancy rate. Multivariate logistic regression analysis suggested that the clinical pregnancy rate (adjusted OR 1.190) and live birth rate (adjusted OR 1.171) of the expected high ovarian response group were higher than those of the normal ovarian response group. In terms of maternal and infant outcomes, the incidence of very preterm delivery in the normal ovarian response group was higher than that in the expected high ovarian response group (0.86% vs. 0.16%, adjusted OR 0.131). Other maternal and infant outcomes were not significantly different.
Conclusion
For patients with expected high ovarian response and regular menstrual cycles undergoing natural FET cycles, the clinical and perinatal outcomes are reassuring. For patients with normal ovarian response, perinatal care should be strengthened during pregnancy to reduce the risk of premature birth.