Obesity Affects Egg Quality, Study Finds

a blog by Claire, September 13, 2012

A new study sheds light on why obesity affects fertility treatment success. Researchers found that eggs from obese women undergoing in vitro fertilization (IVF) were of poorer quality with more than one spindle and disorganized chromosomes.

The study, which was published in the journal Human Reproducton was conducted by researchers at Brigham and Women's Hospital, who examined 276 mature human eggs that failed to fertilize from women who were undergoing IVF. Of these eggs, 105 were from severely obese women with a body mass index (BMI) between 35 and 50.1. There were 171 eggs were from women with a normal BMI, defined as between 18.5 and 24.9.

In a woman's egg, there is a meiotic spindle, which is a critical component involved in organizing chromosome pairs so a proper division of the pairs can occur as the egg is developing. An abnormal spindle can predispose the egg to being chromosomally abnormal. Eggs that have the best chance of fertilizing and supporting embryo development are mature eggs with one spindle upon which is attached one organized set of chromosomes, according to the researchers.

The study found that the eggs from severely obese women were more likely to have multiple spindles and disorganized chromosomes, with nearly 60 percent of the eggs from the severely obese group having two spindles compared to only 35 percent of the eggs from the normal BMI group. Also, 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 did.

Because the study only used eggs from women who received ovarian stimulation for IVF, the results cannot be applied for all eggs. However, with approximately one third of women of childbearing age battling obesity, it's worth reminding women to lose weight before trying to conceive and especially before undergoing fertility treatment such as IVF.

Read Lose Weight for Fertility or IVF