Maternal Weight Affects How Embryos Develop

November 24, 2014

Being overweight can affect fertility, and now there is evidence that maternal weight at conception impacts how a fertilized egg divides and grows.

The embryos of overweight or obese women tend to be smaller and develop differently than those of normal weight women, offering more evidence supporting the importance of maternal weight on conception.

The researchers found a number of distinct differences between the embryos of women who are overweight or obese at the time they conceive and those of women with a healthy weight.

Pertinent Points

- Being overweight or obese at the time of conception could impact the earliest development of an embryo.

- The biochemistry of embryos from overweight or obese women is also altered, with decreased glucose intake and increased triglyceride content.

Publishing in the journal Human Reproduction, the researchers said their study results provide strong evidence for a direct link between a mother’s body weight and the ability of their fertilized eggs to divide and grow.

Besides observing that the eggs from overweight or obese women were significantly smaller in diameter than eggs from women with a healthy BMI, the researchers found that the eggs from overweight and obese women were less likely to reach the blastocyst stage. In addition, when the embryos from overweight and obese women did reach the blastocyst stage, the researchers found that they did so an average 17 hours faster than comparable embryos from women of a healthy weight. The accelerated early development meant the blastocysts had fewer cells, with the outermost layer being the most effected.

The researchers also documented alterations in the biochemistry of the embryos from overweight and obese women, including a significantly reduced intake of glucose and a significant increase in triglyceride content.

The study relied on women seeking fertility treatment and was conducted using the supernumerary embryos that were not selected for IVF treatment.

"What we have found here, is that being overweight at conception does appear to result in changes to the embryo at a very early stage, and that these changes are most likely the result of the conditions in the ovary in which the egg matured,” said study author Roger Sturmey, PhD, from the Hull York Medical School's Centre for Cardiovascular and Metabolic Research at the University of Hull, in a news release. "These changes may reduce the chances of conception for overweight women, and may even have long-term health implications for the children of overweight and obese women."