Obese women undergoing in vitro fertilization (IVF) are significantly more likely to contain structural chromosomal abnormalities in their eggs than those belonging to women with a healthy weight. Being obese is known to affect IVF conception, pregnancy, and birth. The results from a recent study published in the journal Human Reproduction could explain why these women have a much lower IVF success rate than women who are of a healthy weight.
A critical part of an egg’s structural formation is the meiotic spindle, which is involved in the organization of the chromosome pairs. The spindle acts so that a proper division of the pairs can occur as the egg developments. Mature eggs with a single spindle and a complete set of organized chromosomes have the best chance of fertilization.
Researchers from Boston’s Brigham and Women’s Hospital examined mature eggs had failed to fertilize during IVF treatment from both obese women and women who were of a health weight. 105 mature eggs came from 47 severely obese women (body mass index (BMI) above 35), and 171 eggs came from 90 women with a healthy weight (BMI ranging between 18.5 and 25).
The results found that 60 percent of the eggs from the obese women had two spindles. Eggs from women with a healthy BMI had approximately half as many eggs with two spindles (35 percent). In addition, when looking at the eggs found with only one spindle, researchers noticed that for the obese women, approximately one third of the eggs had disorganized chromosomes. Comparatively, only nine percent of eggs containing one spindle from women with a healthy BMI had disorganized chromosomes.
Since all of the eggs studied in the research were from unsuccessful IVF procedures, further research is required to see if the results can be applied to other women, obese and healthy, with infertility. For more information regarding the study, click here.