Ketoacidosis is the build-up of ketones (a by-product of rapid fat breakdown in the body) and can be life-threatening if left untreated. This would generally not occur unless glucose levels were very elevated over a longer period where the cells, needing fuel, rapidly break down fat to help keep the body alive. At that point, one may be in a diabetic coma. In pregnancy, it is important to prevent ketoacidosis, so ketone bodies do not form, as they can cross the placenta and be toxic to the fetus. Symptoms may include fruity-smelling breath, high blood sugar, excessive thirst, frequent urination, nausea, and vomiting.  If concerned, you can buy strips at the pharmacy to test urine for the presence of ketones.