COMPARISON OF MODIFIED NATURAL CYCLE AND HORMONALLY CONTROLLED FROZEN EMBRYO TRANSFER IN OVULATORY VERSUS NON-OVULATORY PATIENTS: A RETROSPECTIVE SINGLE-CENTER STUDY

Document Type

Conference Proceeding

Publication Date

12-1-2025

Publication Title

Fertil Steril

Keywords

chorionic gonadotropin, estrogen, follitropin, gonadorelin agonist, letrozole, progesterone, adult, blastocyst, cohort analysis, conference abstract, controlled study, embryo transfer, endometriosis, female, gestational age, human, low drug dose, luteal phase, luteinizing hormone release, major clinical study, male, obstetric delivery, ovarian reserve, ovulation, people by smoking status, pregnancy, pregnancy rate, preimplantation genetic screening, retrospective study, smoking, spontaneous abortion

Abstract

OBJECTIVE: To compare reproductive outcomes between modified natural cycle frozen blastocyst transfer (NC-FET) in ovulatory patients and hormonally controlled FET (HC-FET) in non-ovulatory patients. MATERIALS AND METHODS: This single-center retrospective cohort study included 857 patients (596 ovulatory and 261 non-ovulatory) who underwent 908 FET cycles (637 in ovulatory patients and 271 in non-ovulatory patients) between January 2006 and December 2024, excluding donor blastocysts and biopsied blastocysts for preimplantation genetic screening. Ovulatory patients underwent modified NC-FET, with human chorionic gonadotropin (HCG, 10,000 IU) administered on the day of LH surge, followed by luteal phase support with vaginal micronized progesterone two days later, with blastocyst transfer seven days after the LH surge. Non-ovulatory patients underwent HC-FET with one of two protocols. Estrogen/progesterone/with or without gonadotropin-releasing hormone agonist with blastocyst transfer on the sixth day of progesterone administration or Letrozole/low dose FSH/HCG with blastocyst transfer on the eighth day of HCG administration. Outcomes included implantation, clinical pregnancy, miscarriage, and delivery/ongoing pregnancy rates, as well as gestational age. Statistical significance was defined as p < 0.05. Generalized estimating equations accounted for more than one FET per patient and logistic and linear regression adjusted for confounders (age, BMI, smoking status, infertility type, male factor infertility, endometriosis, and diminished ovarian reserve). Stratified analysis was performed by age (<35, 35-38, 38-40, >40) and per patient. RESULTS: In per-cycle analysis, ovulatory patients had a significantly higher mean age (34.8+4.1 vs. 33.0+4.1 years, p = 0.001), higher percentage of smokers (38.3% vs. 21.1%, p = 0.001) and lower mean BMI (25.7+5.8 vs. 28.4+7.3kg/m2, p = 0.001) compared to non-ovulatory patients. Implantation (44.1% vs. 49.9%, p = 0.300), clinical pregnancy (58.7% vs. 55.0%, p = 0.740), miscarriage (4.0% vs. 7.3%, p = 0.110), and delivery/ongoing pregnancy rates (51.8% vs. 45.8%, p = 0.095) were comparable between NC-FET and HC-FET groups, respectively. In addition, there were no significant differences in mean gestational age between the two groups, respectively (36.0+6.9 vs. 34.9+8.6 weeks, p = 0.280). Adjusted [Adjusted OR (95%CI): Clinical pregnancy: 0.99 (0.57-1.71); Miscarriage: 2.42 (0.46-12.84); Delivery/ongoing pregnancy: 0.76 (0.44-1.29)] and stratified analyses by age and per patient also revealed no significant differences in reproductive outcomes between the two groups. CONCLUSIONS: Modified NC-FET cycles in ovulatory patients are non-inferior to HC-FET cycles in non-ovulatory patients, supporting individualized treatment approaches. Such findings support tailoring FET protocols based on ovulatory status without compromising success. IMPACT STATEMENT: In ovulatory patients, the modified NC-FET cycle is effective, simpler, more physiologic, and patient-friendly than HC-FET. SUPPORT: Nothing to disclose

Volume

124

Issue

6

First Page

e264

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