An international study published in the journal Diabetes points out that a mom's poor diet during pregnancy may alter the child's DNA and turn on a "fat switch" which leads to a greater chance of the child becoming obese at 6 or 9 years old. As stated by Prof. Keith Godfrey from the University of Southampton, "this study indicates that measures to prevent childhood obesity should be targeted on improving a mother’s nutrition and her baby’s development in the womb". The study also finds that this effect was independent as to whether the mother was slim or heavy. Mom's diet during pregnancy has a high impact on the child's weight and chances of the child becoming obese.

See abstract:

http://diabetes.diabetesjournals.org/content/early/2011/04/04/db10-0979.abstract