When the Mom and dad do not properly prepare their bodies to produce a healthy child, the mother always suffers also. The body will give its self to save the baby the best it can. The baby can be no better off than the mother at anytime and suffers equally. Mom needs a clean body and well nourished body, all signs of ilnes during pregnancy is a sign Mom was lacking proper nutrients and could also have toxic and constipation problems.
With this I would suggest at the very least it is casued by constipation.