This is very good question and quite a challenging one as there is very little known about it. The disorder you are referring to is known as gastroshisis and from what I’ve learned it may have something to do with high estrogen (female sex homone) levels in the women giving birth. Apparently this occurs more in younger and first time mothers who are believed to have higher levels of estrogen at the beginning of pregnancy. Some scientists think that these high estrogen levels can cause blood clots and these blood clots may affect the development of the baby by releasing a substance known as palmitic acid. Also, things such as increased alcohol intake, smoking and exposure to some chemicals (atrazine, a weed-killer for example) are all thought to be involved. However, at the moment this is just a very educated guess and it seems that there is not much really known for sure.
I hope this answers your question, if not please let me know and I will do my best to make everything as clear as possible!