Diabetic ketoacidosis (DKA) during pregnancy is a rare but very serious complication that requires early recognition and treatment to prevent severe complications. Here we present three cases in which DKA occurred during normoglycaemia, demonstrating the importance of early recognition. In pregnancy, DKA can occur at lower blood glucose levels than usual due to several pregnancy-related factors, such as altered metabolism, increased insulin resistance, lower buffering capacity related to chronic hyperventilation and hunger. Symptoms that are common during pregnancy, such as vomiting, may be missed as a first sign of DKA. In patients with type 1 diabetes mellitus (especially those on continuous subcutaneous insulin infusion) insulin administration must never be discontinued, as this prevents lipolysis and ketone formation. Physicians and patients need to be aware of the risks and management of DKA in pregnancy.