(HealthDay News) – Oocytes from severely obese women undergoing in vitro fertilization display significant spindle abnormalities, which may contribute to poor reproductive outcomes, according to a study published online Sept 11 in Human Reproduction.

To investigate the potential underlying mechanisms associated with poor reproductive outcomes in obese patients, Ronit Machtinger, MD, of Brigham and Women’s Hospital and Harvard Medical School in Boston, and colleagues conducted a study involving severely obese patients treated in a hospital-based infertility clinic. Cytoskeletal and chromosome organization of 276 oocytes that failed to fertilize were compared from severely obese patients (105 oocytes from 47 women) and from patients with normal body mass index (BMI) (171 oocytes from 90 women).

Compared with oocytes from women in the normal BMI group (18.5–24.9kg/m²), the researchers found that significantly more oocytes from severely obese women (BMI, 35–50.1kg/m²) exhibited two spindles (58.9 vs. 35.1%; odds ratio, 2.68). Of the oocytes with a single spindle, there was a significantly higher prevalence of disarranged spindles with nonaligned chromosomes among severely obese versus normal-weight women (28.6 vs. 8.6%; odds ratio, 4.58).

“In summary, our observations provide novel insight into a possible cause for the reduced fertility in severely obese patients,” the authors write. “The high rates of spindle abnormalities we document suggest that, in these patients, at least a proportion of the ‘mature’ oocytes (based on the presence of a polar body) may have a compromised quality that precludes normal completion of fertilization.”

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