[The effects of high risk of ovarian hyperstimulation syndrome and duration of embryo cryopreservation on perinatal outcomes of single live births in the first frozen embryo transfer cycle after whole embryo cryopreservation]

Objective: To investigate the effects of high risk of ovarian hyperstimulation syndrome (OHSS) and duration of embryo cryopreservation on perinatal outcomes of the first frozen-thawed cycle after whole embryo cryopreservation. Methods: The clinical data of 1 804 patients who underwent the first frozen-thawed cycle after whole embryo cryopreservation and achieved singleton live births in the Reproductive Center of the Third Affiliated Hospital of Zhengzhou University from January 2016 to June 2021 were retrospectively analyzed. According to whether there was high risk of OHSS in the oocyte retrieval cycle, the patients were divided into high-risk group (n=790) and non-high-risk group (n=1 014). The baseline data and perinatal outcomes were compared between the two groups. Multivariate linear regression was applied to analyze the relative factors affecting neonatal weight. And the high-risk group was divided into three subgroups according to different cryopreservation time: the embryos of 96 cycles with a cryopreservation time less than 60 days were defined as group A; the embryos of 587 cycles with a cryopreservation time around 60 to 120 days were defined as group B; the embryos of 107 cycles with a cryopreservation time more than 120 days were defined as group C. The perinatal outcomes were compared among the three groups. The measurement data in this study were represented by［M（Q₁，Q₃）］. Results: The female age in the high-risk group was 30.0 (27.0, 32.0) years old, which was lower than that in the non-high-risk group 31.0 (29.0, 34.0) (P<0.001). The male age in high-risk group was 30.0 (28.0, 33.0), lower than that in non-high-risk group 32.0 (29.0, 35.0) (P<0.001). The birth weight of high-risk group [3 500.0 (3 200.0,3 800.0) g] was higher than that of control group [3 400.0 (3 150.0,3 800.0) g](P=0.045). Multivariate linear regression analysis showed that female BMI was correlated with neonatal weight, β (95%CI) was 15.37(8.33, 22.41) (P<0.001), and the high risk of OHSS was not correlated with neonatal weight, β (95%CI) was 19.40 (-38.07, 76.87) (P=0.508). There was significant difference in the incidence of low birth weight and very low birth weight among groups A, B and C (all P values<0.05), and the incidence of low birth weight and very low birth weight in group C was higher than that in group B (all P values<0.017). Conclusions: The risk of adverse perinatal outcomes in high-risk OHSS patients who underwent the first frozen-thawed cycle after whole embryo cryopreservation was not increased. However, prolonged cryopreservation of embryos may lead to increased risk of low birth weight and very low birth weight.