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 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 molecule drugs are more easily transferred into the fetus through the placenta, and the drugs can also be absorbed from the gastrointestinal tract 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, the glomerular filtration rate of fetus is low, and 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 harmful drug effects, it may cause intrauterine growth retardation (IUGR), low birth weight, abnormal functional behavior and premature birth. 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; treatment can be postponed if it can be postponed; when it has 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 drugs that have an impact on the fetus, she should use them after fully weighing the pros and cons, adjusting the dosage at any time according to her condition and stopping them in time. 5. The application of Chinese medicine during pregnancy is mainly based on our ancient medical knowledge of the dangers of medication during pregnancy, but there are many differences in the contraindications to pregnancy recorded in the important medical literature over the ages. The main should prohibit the aconite, eucommia, croton, coriander, halberd, leech, gadfly, centipede, androgynous, estrogen, petunia, musk, etc.