Gingivitis during pregnancy is a common and frequent disease in women during pregnancy, due to the increase in female hormone levels, the existing chronic inflammation of the gums aggravates, making the gums swollen or forming tumor-like changes, which can reduce or subside on their own after delivery. Although gingivitis during pregnancy may heal spontaneously after delivery, it is still harmful, affecting the chewing, digestion and absorption of food in pregnant women, and in severe cases, the tumor may be too large and interfere with eating or cause secondary infection by biting through. It has been reported in the literature that periodontal disease in pregnant women can affect the normal development of the fetus, especially causing premature birth and low birth weight babies. A growing number of studies have confirmed that periodontal disease is highly associated with adverse outcomes in pregnancy and is more likely to cause preterm birth than smoking or alcohol consumption. So, what causes gingivitis in pregnancy? There are many causes of gingivitis during pregnancy, but plaque microorganisms remain the direct cause of gingivitis during pregnancy. If a pregnant woman does not pay attention to oral hygiene, plaque and tartar accumulate near the gingival margin, which can easily lead to gingival inflammation; if there are also food inclusions and poor restorations, it is more likely to aggravate the inflammation of the gums. Pregnancy is not a direct cause of gingivitis; if there is no plaque present, pregnancy does not cause inflammation of the gums. The occurrence of gingivitis during pregnancy is only due to the change in the level of sex hormones during pregnancy and the increased response of the gums to local stimuli aggravating or changing the characteristics of the existing chronic inflammation of the gums. Especially after the 6th month of pregnancy, sex hormone levels increase and can reach 10 times the usual level, which makes capillary congestion and inflammatory cells increase, aggravating the gingival response to plaque. The first step in determining if you have gingivitis during pregnancy is to know if you had chronic gingivitis prior to pregnancy. Patients generally have varying degrees of chronic gingivitis prior to pregnancy, with significant symptoms beginning in the second to third trimester of pregnancy and peaking by the eighth month. The gums are bright red or dark red, flaccid and shiny, swollen, hypertrophic, bleed easily, and are generally painless. When gingivitis in pregnancy occurs it should be treated as early as possible and systemic medication should be avoided as much as possible to avoid affecting fetal development. 1, first remove local irritants, because in pregnancy, the action should be gentle, try to reduce bleeding and pain. 2.Conduct careful oral hygiene education, strictly control plaque and maintain treatment. The main causative agent of gingivitis during pregnancy is Prevotella intermedia, which is due to the increase of progesterone during pregnancy, and the number and proportion of Prevotella intermedia will increase with the increase of progesterone level in the body during pregnancy, but will decrease after delivery. The methods to control plaque are: (1) Mechanical methods: brushing (Bass brushing method), flossing and interdental brushing to clean teeth. (2) Other methods: oral rinse with mouthwash, mouthwash should choose a rinse with less irritation and does not affect the development of the fetus. 3.If the inflammation is heavy, use 1% hydrogen peroxide solution and saline rinse. 4.For larger gingival tumors in pregnancy, if they have prevented eating, surgery can be considered to remove them, but surgery should be chosen within 4~6 months of pregnancy as much as possible to avoid causing abortion or premature delivery. Therefore, the original chronic gingivitis should be treated in time before pregnancy, and strict control of plaque during pregnancy can greatly reduce the occurrence of gingivitis during pregnancy.