The study carried out by Hull York Medical School (HYMS) with the Hull IVF Unit, found being overweight at conception appears to result in changes to the embryo at a very early stage.
Eggs were smaller, less likely to reach a crucial stage of development after fertilisation, called the blastocycst, and those that did reach it contained less glucose - an important food for early stage embryos - and more fat.
They also showed altered metabolism of amino acids, the building blocks of cells, muscles and tissues.
Dr Roger Sturmey, from the HYMS Centre for Cardiovascular and Metabolic Research, said the changes were most likely the result of the conditions in the ovary in which the egg matured.
He said the changes could reduce the chances of overweight women conceiving, adding: “The research highlights the importance of a healthy pre-pregnancy body weight for not only optimising the chances of chances of conception, but also for safeguarding maternal and child health.”