One third of American women of childbearing age are battling obesity, a condition that affects their health and their chances of getting pregnant. Obese women often have poor reproductive outcomes, but the reasons why have not been clearly identified. Now, a novel study gains further insight into the underlying mechanisms. The study was published online on September 11 in the journal Human Reproduction.
According to the authors, 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 severely obese women have a much greater chance of having eggs with multiple spindles and disorganized chromosomes. Specifically:
- 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.
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.