Study design and patients
This study retrospectively collected and evaluated the clinical data of 8903 patients after FET at the Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, who were patients between January 2017 and October 2019. All women were between the ages of 20 to 40 years with a body mass index (BMI) of no more than 35 kg/m2, who underwent their first FET during their first in vitrofertilization/intracytoplasmic sperm injection cycle at our centre.
Women were excluded from this study if they (i) underwent frozen-thawed oocyte cycle or preimplantation genetic testing cycles, (ii) were diagnosed with premature ovarian insufficiency or a decreased ovarian reserve, (iii) had a history of unilateral oophorectomy, recurrent spontaneous abortion or severe intrauterine adhesion, (iv) had medical conditions that contraindicated assisted reproductive technology or pregnancy, and (v) were diagnosed with hypertension, diabetes, abnormal renal function, uterine malformation or abnormal parental karyotypes. This study was approved by the Ethics Committee of the Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University (2021-25).
All women were assigned to either PCOS or control groups. A diagnosis of PCOS was based on Rotterdam diagnostic criteria and if at least two of the following criteria were present: HA (hyperandrogenemia, defined as total testosterone levels above 48.1 ng/dL, and hirsutism with a total score ≥8 according to the Ferryman–Gallwey score); OA (defined as a delay of >35 days or < eight spontaneous hemorrhagic episodes/years); PCO (defined as ≥12 small follicles measuring 2–9 mm in at least one ovary or ovarian volume ≥10 cm3)15. Patients with PCOS were categorised into four phenotype groups according to Rotterdam criteria as follows16: phenotype A: HA+OA+PCO; phenotype B: HA+OA; phenotype C: HA+PCO; and phenotype D: OA+PCO.