Are you on any kind of medication for morning sickness? Sometimes that medication (while admirable in purpose) can cause itching. I've also heard of a rash that some women get in pregnancy, but unfortunately like mummytwo, I can't remember what it's called. You might call your doctor and ask about it.
Its a rare pregnancy rash probably.. a girl i knew had it it was lots of splotchy red bumps.. just ask your doctor to make sure though, even my mom had it when ahe was pregnant with me.. i cant remember what its called though