Dr. Kenneth Jones, USC San Diego, received the Hartwell Foundation Grant to study women who are carrying babies with gastroschisis. http://ucsdnews.ucsd.edu/newsrel/awards/04-08KennethLyonsJones.asp
In this article he attributes all of it to age and fast food/Western style processed food. The age, his assistant explained to me, is because they are young and make unhealthy food choices
There is a lot of speculation as to the cause. However, in the medical literature none of the speculated causes include fast food. There's a somewhat technical article on the condition on emedicine.com. Sign in and take a look.