Pregnant women may suffer from irritating rashes. Often there is no obvious cause for these, though they may be due to allergies to particular foods or soaps or perfume. If the rash lasts for more than a day or two, consult your doctor. If you get a rash in your groin or under your breasts, it may be caused by sweat irritating your skin. This type of rash is more common in women who are overweight. It is best treated by frequent washing and applying calamine or talc.