Association between body mass index and ovarian morphology in Nigerian women with polycystic ovary syndrome: A comparative transvaginal sonographic study

Background: Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting women of reproductive age and is frequently associated with obesity and metabolic complications. However, the relationship between body mass index (BMI) and ovarian morphological abnormalities remains unclear, particularly among African women. This study assessed the association between BMI and ovarian morphology among Nigerian women with PCOS using transvaginal ultrasonography. 
Methods: A prospective comparative cross-sectional study was conducted among 205 women attending the Fertility Clinic of the Federal Medical Centre, Onitsha, Nigeria. Participants comprised 105 women with PCOS and 100 apparently healthy controls. Anthropometric measurements were obtained, and BMI was calculated. Transvaginal ultrasonography was used to assess ovarian volume, antral follicle count, and stromal thickness. Data were analysed using independent samples t-test, chi-square test, and Pearson’s correlation coefficient, with statistical significance set at p < 0.05.
Results: Women with PCOS had significantly higher mean BMI than controls (25.56 ± 4.87 vs 23.15 ± 3.37 kg/m²; t(203) = −4.10, p < 0.001). Overweight and obesity were more common among women with PCOS (20.0% and 21.9%, respectively) compared with controls (17.0% and 4.0%). Ovarian volume, antral follicle count, and stromal thickness were significantly greater among women with PCOS than controls (all p < 0.001). However, BMI was not significantly correlated with ovarian volume, antral follicle count, or stromal thickness in either group (all p > 0.05). 
Conclusion: Women with PCOS had higher BMI and more pronounced ovarian morphological abnormalities than healthy controls. Nevertheless, BMI was not associated with ovarian structural parameters, suggesting that obesity may contribute more to the metabolic phenotype of PCOS than to ovarian morphology. Transvaginal ultrasonography, integrated with clinical and biochemical assessment, remains essential for PCOS evaluation.