Introduction
Polycystic ovary syndrome (PCOS) is considered a common endocrine disorder in women of reproductive age1, affecting 6–21% of women worldwide2. Characteristics of PCOS include obesity, insulin resistance, hyperandrogenism, anovulation and polycystic ovaries3. Due to endocrine disorders and anovulation in women with PCOS, which lead to infertility4, such women usually require assisted reproductive technology (ART) to become pregnant.
Applying PCOS diagnostic criteria, four phenotypes are distinguished: phenotype A: coexistence of clinical hyperandrogenism/hyperandrogenemia (HA), oligomenorrhea/anovulation (OA) and polycystic ovaries (PCO); phenotype B: HA and OA without PCO; phenotype C: HA and PCO with regular ovulatory cycles; and phenotype D: OA coexisting with PCO2. Patients with different PCOS phenotypes show different ovarian responses to controlled ovarian hyperstimulation (COH)5, which might contribute to different pregnancy outcomes6. The previously published literature has mainly described pregnancy outcomes in patients with different PCOS phenotypes after fresh embryo transfer6,7; patients with PCOS are prone to ovarian hyperstimulation syndrome (OHSS) during or after COH8. Clinically, a fresh embryo transfer is usually cancelled to reduce the risk of OHSS9. However, it has been reported that frozen-thawed embryo transfer (FET) can not only reduce the risk of OHSS, but also improve ART outcomes10. Recently, a multi-centre randomised controlled trial of infertile women with PCOS suggested FET led to a higher rate of live births, and a lower risk of abortion than did fresh embryo transfer11. FET allows time for the use of preimplantation genetic technology12. Therefore, a considerable number of infertile patients choose to undergo FET. However, PCOS is associated with adverse pregnancy outcomes, including an increased risk of abortion, premature delivery, pre-eclampsia and even neonatal outcomes13,14. After removing the effect of COH on patients, studying the pregnancy outcomes of patients with different PCOS phenotypes after FET may better reflect the impact of different PCOS phenotypes on ART outcomes. Subsequent clinical management, which might optimise pregnancy outcomes, could then be carried out based on different PCOS phenotypes.
The aim of this study was to assess the effect of various PCOS phenotypes after FET on pregnancy outcomes.