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Updated: May 28, 2025
Isolation of Small Preantral Follicles from the Bovine Ovary Using a Combination of Fragmentation, Homogenization, and Serial Filtration
Published on: September 27, 2022
Smaller follicle diameter improves outcomes in natural LPOS: a retrospective cohort study
Jifan Tan1,2, Sirui Liao1,2, Dehai Gan1,2
1Reproductive Medicine Center, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.
Background:
This study aimed to investigate the optimal follicular diameter at the initiation of luteal-phase ovarian stimulation (LPOS) protocol after natural ovulation to achieve better laboratory outcomes.
Methods:
This retrospective cohort study analyzed 286 in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles in patients who began the LPOS protocol after natural ovulation. Patients were categorized into three groups based on follicle diameter at initiation: small diameter follicles (SDF, < 5 mm, n = 74), medium diameter follicles (MDF, 5.0-7.9 mm, n = 140), and large diameter follicles (LDF, ≥ 8 mm, n = 72). Linear regression analysis was used to assess the relationship between initial follicle diameter and laboratory outcomes.
Result:
Significant differences were noted in anti-Müllerian hormone (AMH), body mass index (BMI), and initial gonadotropin (Gn) dose among the groups. Primary outcomes included oocyte retrieval rate (SDF vs. MDF vs. LDF: 0.92 ± 0.88 vs. 0.68 ± 0.48 vs. 0.58 ± 0.54, p = 0.004), mature oocyte retrieval rate (0.78 ± 0.74 vs. 0.58 ± 0.43 vs. 0.51 ± 0.50, p = 0.01), and 2PN rate (0.58 ± 0.68 vs. 0.44 ± 0.40 vs. 0.36 ± 0.43, p = 0.03) in the SDF group were significantly higher than those in the MDF and LDF groups. Multivariate regression analysis, adjusting for potential confounders such as age, AMH levels, baseline follicle-stimulating hormone (FSH) levels, BMI, and initial Gn dosage, revealed negative correlations between the initial follicle diameter and oocyte retrieval rate (p = 0.02), mature oocyte retrieval rate (p = 0.02), and 2PN rate (p = 0.04).
Conclusions:
Oocyte retrieval rate, mature oocyte retrieval rate, and 2PN rate decreased significantly with increasing follicle diameter at the initiation of LPOS. The optimal laboratory outcome was achieved with an initial follicle diameter of less than 5 mm.
