Why obese women have difficulty conceiving from IVF
Washington: Researchers have gained further insight into why obese women often have poor reproductive outcomes.
Catherine Racowsky from Brigham and Women’s Hospital (BWH), and performed by Ronit Machtinger examined 276 mature human eggs that failed to fertilize from women who were undergoing in vitro fertilization (IVF) procedures.
Of these, 105 eggs were from severely obese women, defined as having a body mass index (BMI) between 35.0 and 50.1 kg/m2, and 171 eggs were from women with a normal BMI, defined as between 18.5 and 24.9 kg/m2. BMI is calculated from a person’s height and weight and is considered a reliable indicator of body fatness for most people.
“This study is the first to shed light on how BMI might adversely affect egg quality in women,” Dr. Racowsky said.
“These observations provide novel insight into a possible cause for the reduced likelihood of success with IVF in severely obese women,” she said.
According to Dr. Racowsky, in order for an egg to have the best chance of fertilizing and supporting embryo development, it should be “mature” with one spindle (a critical egg structure) on which is attached one organized set of chromosomes.
This study found that severely obese women have a much greater chance of having eggs with multiple spindles and disorganized chromosomes.
Nearly 60 percent of the eggs from the severely obese group had two spindles, while only 35 percent of the eggs from the normal BMI group had two spindles.
Among the eggs with one spindle, nearly 30 percent of the eggs from the severely obese group had disorganized chromosomes, while only 9 percent of the eggs from the normal BMI group had disorganized chromosomes.
Dr. Racowsky points out that this study only used eggs that were stimulated through IVF and that failed to fertilize, so it is not known if these results can be broadly applied to all eggs.
The study has been published online in the journal Human Reproduction.