Every family wants 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 most of the rest are caused by genetic and environmental factors. Medications should be used with caution during pregnancy. Most drugs can enter the fetus through the placenta, especially some fat-soluble drugs of 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, because of the imperfect development of fetal liver and the lack of drug metabolizing enzymes, the detoxification ability of drugs is low, and the glomerular filtration rate of fetus is low, the excretion of drugs and degradation products is delayed, so drugs are easy to accumulate in the fetus. Therefore, drugs are likely 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”. The “all” means that the harmful drugs can destroy all or part of the embryonic cells, resulting in the early death of the embryo, leading to miscarriage; “none” means that the harmful drugs do not damage the embryo or only damage a small number of cells, but the cells at this stage have the ability to differentiate in multiple directions, which can compensate and repair the damaged cells. The embryo can continue to develop without abnormalities. Therefore, this period is a safe period for drug use. If the drug does affect the fertilization rate, it will be eliminated naturally before implantation. 2.Weeks 4 to 9 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. 3, the 10th week of pregnancy to delivery: this period is the stage of fetal growth and functional perfection, but the nervous system, reproductive system is still continuing to differentiate. When subjected to the effects of harmful drugs, it may cause intrauterine growth retardation, low birth weight, abnormal functional behavior, premature birth, etc. Since improper use of drugs during pregnancy may cause serious consequences, the following principles of drug use 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 three months of pregnancy; drugs that can be used or can be discontinued should be used or discontinued; drugs that can be used or discontinued should be used as much as possible, and treatment that can be postponed should be postponed; when they have to be used, drugs with clear instructions on drug metabolism should be used as much as possible. 2, according to the degree of drug may have different effects on the fetus, choose the drug that has the least impact on the fetus, can be treated with drugs alone to avoid the combination of drugs. 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 to have an impact on the fetus drugs, should be used after fully weighing the pros and cons, according to the condition at any time to adjust the dosage, timely discontinuation of drugs. 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 for pregnant women with the drug and may be considered if the pregnant woman is seriously ill or threatened with death; Class X: Studies in either 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, the antiviral drug triazolyl nucleoside. There are drug classifications listed in the drug instructions, and certain drugs have two different risk levels, one for common doses and the other for extraordinary doses, which can be referenced during application. The use of Chinese medicine during pregnancy also requires extra caution, and the application 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 aconite, sophora, croton, coriander, halberd, leech, gadfly, centipede, androgynous, female yellow, petunia, musk, etc.