Introduction/Background The incidence of early stage endometrial cancer(EC) and endometrial atypical hyperplasia(EAH) has been increasing in recent years. For EC patients who desire to preserve fertility, high-dose progestin have been applied as classical treatment regimen. Our previous studies reported that the median treatment duration to achieve complete response (CR) were 31.1 weeks .For these patients, it is urgently needed to solve fertility problem. We aimed to investigate the clinical features, pregnancy complications and outcomes in EC and EAH patients after CR of fertility preserving treatment.

Methodology This was a retrospective analysis of 481 patients with EC and EAH after fertility preserving treatment from January 2015 to April 2023. These patients meeting one of the following criteria: (1) natural pregnancy at least three cycles; (2) ovulation induction at least three cycles; (3) perform at least one cycle of IVF-ET.

Results A total of 281 patients achieved pregnant (with 18 repeated pregnancies), including 188 EAH and 93 EC patients. The overall cumulative pregnancy rate was 62.16%. The live birth rate and miscarriage rate were 42.83% and 12.89%.

A total of 269 successful deliveries have been achieved, including 69 cases of natural pregnancy, 53 of ovulation induction, and 147 of IVF-ET. Among all patients who have successfully delivered, the incidence rates of gestational hypertension, GDM and PGDM, thyroid disease complicating pregnancy, placenta adhesion/implantation, placental abruption, placenta previa, FGR, cervical insufficiency, and preterm birth were 13.75%,14.87%, 3.35%, 11.15%, 1.12%, 1.86%, 1.49%, 5.58% and 14.87% respectively.

By multivariate analysis, hysteroscopy frequency ≥ 5 times before pregnancy was independent risk factors for placenta accreta/implantation. Twin pregnancy was independent risk factors for preterm birth.

Conclusion A higher pregnancy rate and live birth rate can be achieved after CR of EC/EAH. There was a positive correlation between the hysteroscopy frequency and placental adhesion/implantation, but no significant correlation with cervical insufficiency.

Disclosures The authors declare no competing interests.