Every family hopes to have a healthy and smart baby, but improper medication during pregnancy may have an impact on the fetus. The World Health Organization estimates that more than 90% of pregnant women have taken various prescription drugs, over-the-counter medications or prohibited drugs during pregnancy. Among children with birth defects, 2% to 3% are caused by drugs, while the rest are mostly caused by genetic and environmental factors. Therefore, medication during pregnancy should be used with caution. Most drugs can enter the fetus through the placenta, especially some fat-soluble large and small molecules are more easily transferred into the fetus through the placenta, and drugs can also be absorbed in small amounts from the stomach and intestines through the fetus swallowing amniotic fluid. In addition, due to the imperfect development of the fetal liver, the lack of drug metabolizing enzymes and the low detoxification ability of drugs, the low glomerular filtration rate of the fetus, the delayed excretion of drugs and degradation products, so the drugs are easy to accumulate in the fetus. Therefore, drugs are prone to affect the fetus. The effect of drugs on the fetus depends on the developmental stage of the fetus at the time of drug use, and the consequences of drug use at different times are different: (1) before fertilization to the end of the fourth week of pregnancy: the effect of drugs on the embryo during this period is “all” or “none”. (1) from the pre-fertilization period to the end of the fourth week of pregnancy: the effect of drugs on the embryo during this period is either “total” or “none”, i.e. the harmful drugs can destroy all or part of the embryonic cells, resulting in early death of the embryo and miscarriage. The embryo can continue to develop without abnormalities. If the drug does affect the fertilization rate, it will be eliminated naturally before implantation. (2) The fourth week to the ninth week of pregnancy: this is the period when the important organs of the fetus, such as the central nervous system, heart, eyes, limbs, etc., begin to form, and it is also the most sensitive period to drugs, and the fetus is very susceptible to malformations caused by drugs and other external factors. (3) The 10th week of pregnancy to delivery: This is the period when the fetus is growing and perfecting its functions, but the nervous system and reproductive system are still differentiating. When exposed to harmful drugs, it may cause intrauterine growth retardation (IUGR), low birth weight, abnormal functional behavior and preterm delivery. Since inappropriate use of drugs during pregnancy may have serious consequences, the following principles should be followed: (1) When using drugs, attention must be paid to the size of the gestational week, and caution should be exercised in the first trimester of pregnancy. (2) According to the different degrees of possible effects of drugs on the fetus, choose the drug that has the least effect on the fetus, and avoid combining drugs if they can be used alone. (3) The dose and duration of medication should be strictly controlled, the lowest effective dose should be used as much as possible, and the duration of medication should be as short as possible, and the effect on the newborn should be considered when medication is used during delivery. (4) When the condition of the pregnant woman really needs drugs that have an impact on the fetus, they should be used after fully weighing the pros and cons, adjusting the dosage at any time according to the condition and stopping the drugs in a timely manner. In order to ensure the safe and reasonable use of drugs during pregnancy, many countries have their own medication reference standards and evaluation methods for the safe use of drugs during pregnancy, and implement a grading system for the use of drugs during pregnancy. At present, the clinical use of western drugs in China is based on the U.S. FDA pregnancy drug safety classification. Based on the results of animal tests and clinical trials to evaluate the safety of drugs for humans, the grading standards are: Grade A: It has been confirmed that such drugs have no adverse effects on the human fetus. Only a very few drugs belong to this category, such as thyroxine, folic acid, vitamins, etc.; Grade B: animal experiments have proved to be harmless, but there is no sufficient evidence in humans. Most of the antibiotics commonly used in clinical practice belong to class B drugs; Class C: animal experiments have proven harmful to animal embryos, and there are no relevant studies in humans yet. For example, anti-tuberculosis drugs are commonly used, and this class of drugs is only available when the benefits to the fetus outweigh the harms; Class D: there is clear evidence of harm to the fetus. Such as aminoglycosides, tetracyclines, high-dose vitamins, etc. Despite the hazards, there are absolute benefits when administered to pregnant women, and may be considered if the pregnant woman is seriously ill or threatened with death. Class X: Studies in animals or humans have shown that they can cause fetal abnormalities and this class of drugs is contraindicated in patients who are or will be pregnant. For example, antiviral drugs such as triazolyl nucleoside. In the drug instructions are listed in the drug classification, some drugs also have two different risk levels, one is the commonly used dose level, and the other is the extraordinary dose level, which can be referred to when applied. The application of Chinese medicine during pregnancy is mainly based on our ancient medical knowledge of the dangers of using drugs during pregnancy, but there are many differences in the contraindications to pregnancy recorded in important medical literature over the ages. The main should be prohibited the aconite, eucommia, croton, coriander, macrophyllum, leech, gadfly, centipede, andrographis, estradiolus, petunia, musk, etc.