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. 2025 Jun 18.
doi: 10.1007/s10815-025-03523-4. Online ahead of print.

Comparing programmed, modified natural and natural cycle frozen embryo transfer on obstetric outcomes in polycystic ovary syndrome: a national cohort study

Eun Hee Yu  1   2 , Hyun Joo Lee  1   2 , Jong Kil Joo  3   4 , Yong Jin Na  1
Affiliations

Comparing programmed, modified natural and natural cycle frozen embryo transfer on obstetric outcomes in polycystic ovary syndrome: a national cohort study

Eun Hee Yu et al. J Assist Reprod Genet. .

Abstract

Purpose: Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with adverse reproductive and obstetric outcomes, particularly in pregnancies achieved through assisted reproductive technologies. This study aimed to compare obstetric outcomes among programmed cycle-frozen embryo transfer (PC-FET), modified natural cycle-frozen embryo transfer (mNC-FET), and natural cycle-frozen embryo transfer (NC-FET) in women with PCOS using a nationwide Korean health claims database.

Methods: This population-based cohort study utilized data from the National Health Insurance Service-National Health Information Database of South Korea. A retrospective analysis was conducted on 3,873 PCOS patients with singleton pregnancies following FET between October 2017 and December 2021. Patients were categorized into PC-FET, mNC-FET, and NC-FET groups based on prescription records. Obstetric outcomes were analyzed using logistic regression models adjusted for age and medical comorbidities.

Results: mN-FET was associated with significantly lower rates of miscarriage (23.9%) compared to PC-FET (31.3%) and NC-FET (32.0%), as well as a higher term birth rate (69.6% vs. 61.7% and 60.2%, respectively). mNC-FET also showed significantly lower rates of hypertensive disorders of pregnancy, gestational hypertension, cesarean section, and emergency cesarean section compared to PC-FET. No significant differences were observed between mNC-FET and NC-FET in most obstetric complications.

Conclusion: mNC-FET was associated with favorable obstetric outcomes compared to PC-FET and NC-FET in women with PCOS. These findings suggest that mNC-FET may be an effective and safer endometrial preparation strategy in this population. Further prospective studies are needed to validate these results and optimize FET protocols based on individual patient characteristics.

Keywords: Frozen embryo transfer; Modified natural cycle; National cohort; Natural cycle; Obstetric outcomes; Polycystic ovarian syndrome; Programmed cycle.

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Conflict of interest statement

Declarations. Ethical approval: Individual identifiers within the Korean NHIS database were anonymized. The study procedures were approved by the official assessment panel of the Korean Government and Institutional Review Board (IRB) of Pusan National University Hospital (IRB 2304–015-126), adhering strictly to their guidelines. Since the data were deidentified, the IRB waived the necessity for obtaining informed consent. Conflict of interest statement: The authors declare no financial and non-financial conflicts of interest.

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