A type of diabetes mellitus that can occur when a woman is pregnant. During the pregnancy (usually later in it), the woman may have glucose (sugar) in her blood at a higher than normal level. However, when the pregnancy ends, the blood glucose levels return to normal in about 95 percent of all cases. It MUST be treated carefully by a physician for it is dangerous to both mother and child. If treated properly, there are usually no lasting effects on either. Women who have had an episode of GDM are at higher risk of developing Type 2 diabetes later on.