Obese women are more likely to have egg abnormalities associated with infertility.

Modern reproductive science has unlocked the key to a vast array of fertility problems, and researchers at Brigham and Women’s Hospital have now discovered a possible link between obesity and egg quality.

Obesity has long been associated with poor reproductive outcomes, but the reason has largely been unknown. With one-third of all American women of childbearing age battling obesity, it is a major barrier for many wishing to grow their family.

A new study released earlier this month shows that severely obese women are more likely to have abnormalities in their eggs that can make it impossible for them to be fertilized normally. The abnormalities involve the spindle, a critical egg structure responsible for normal arrangement of the chromosomes. A normal egg must have one spindle organized in a very specific way, with the chromosomes lined up correctly. The study showed that severely obese women have a much greater chance of having eggs with multiple spindles and disorganized chromosomes.

“This study is the first to shed light on how BMI (body mass index) might adversely affect egg quality in women,” said study lead, Catherine Racowsky, PhD, Director of the Assisted Reproductive Technologies Laboratory at Brigham and Women’s Hospital.

In the study, researchers examined close to 300 eggs that failed to fertilize during IVF (in vitro fertilization) in both severely obese women and those with a normal body weight. They found that severely obese women were far more likely to have multiple spindles and abnormally arranged chromosomes within their eggs compared with women who were not overweight.

“These observations provide novel insight into a possible cause for the reduced likelihood of success with IVF in severely obese women,” said Dr. Racowsky. “More research is needed to determine what is causing the spindle abnormalities and disorganized chromosomes.”

Learn more about the Center for Infertility and Reproductive Surgery at Brigham and Women’s Hospital.


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