Bad breath during pregnancy can be caused by pregnancy vomiting, gastrointestinal disorders, gingivitis and other reasons. 1. Vomiting during pregnancy: During pregnancy, the level of estrogen in the body rises, which may cause nausea, vomiting and other pregnancy reactions, resulting in bad breath during pregnancy. 2. Gastrointestinal dysfunction: During pregnancy, the digestive and absorptive functions of the stomach and intestines are affected, which may lead to bad breath during pregnancy. 3. Gingivitis: If you don’t pay attention to oral hygiene during pregnancy, the mouth contains food debris, so that the bacteria overgrowth causes pregnant women to suffer from gingivitis and other oral diseases, which may lead to bad breath in the mouth. During pregnancy, you should pay attention to drink more water, maintain oral hygiene, when the symptoms are serious, you should go to the hospital in time to improve the relevant examination, clear diagnosis and give standardized treatment.