Metronidazole can be taken in the 13th week of pregnancy if there are necessary indications, otherwise it cannot be taken at will. Metronidazole is a nitroimidazole drug, widely used in the treatment of anaerobic infections, aerobic or partially aerobic bacteria are ineffective, obstetrics and gynecology is commonly used in the treatment of bacterial vaginitis or trichomoniasis vaginitis. Metronidazole is a pregnancy category B drug, i.e., there is no certainty of side effects in the control group of early pregnant women, and there is no evidence of risk in middle and late pregnancy. However, 13 weeks of pregnancy is the stage of mid-pregnancy, fetal organs are developing, only because of the need for disease, in the case of adequate medical indications can be under the guidance of a doctor to eat metronidazole, can not blindly use their own medication. No matter what medication is used after pregnancy, caution should be exercised, and blind use of medication may result in adverse consequences.