Bad breath of pregnant women may be caused by tooth decay, or gingivitis, or gastrointestinal problems. There are several causes of bad breath for pregnant women, the common one is caused by tooth decay, if the tooth cavity is not treated in time, the food residue accumulation in the cavity is not removed in time, the bacterial fermentation will appear bad breath. It is also possible that the tooth decay is not treated in time, and the bacteria further infect the nerve of the tooth, causing the pulp tissue to become septic and necrotic, resulting in the odor of dead pulp teeth. Bad breath of pregnant women may also be caused by gingivitis, not timely brushing and rinsing after eating, food residue or soft scale accumulation around the teeth, causing congestion in the gum tissue, bacteria in the plaque causes the gum tissue to overflow pus, and the change of hormone level in the body after pregnancy, easily triggering gingivitis and corrosive bad breath. Bad breath of pregnant women may also be caused by digestive disorders of the gastrointestinal tract. If the diet is irregular during pregnancy, or if you eat meat or protein and legumes, the gastrointestinal tract is disrupted and the food is not completely digested, bad breath will also occur. Therefore, bad breath in pregnant women may be caused by gingivitis due to hormonal changes in the body, or by necrosis of the dental nerve, or by gastrointestinal tract dysfunction.