I. Principles of medication during pregnancy Pregnant women often need to be treated with medication due to some abnormal conditions or diseases. The effect of medication on the fetus varies according to the type of medication. As many drugs can pass freely through the placenta, some of them may cause abnormal fetal development or even fetal malformation. Therefore, in principle, it is better not to use drugs during pregnancy, but if there is a need to use drugs, doctors should pay attention to the following eight principles. 1, the use of drugs must have clear indications and indications. Neither should they be abused, nor should they be used when there is a disease. Pregnant women are affected by the same disease that affects the fetus. Try to use drugs that have been proven to be relatively safe for the embryo and fetus. 2. When using drugs for women of childbearing age, ask about the last menstruation and conception. 3. Drugs that can be used or not should be used as little as possible. Especially in the first trimester of pregnancy, drugs that can be used or temporarily discontinued should be considered not used or suspended. 4, the use of drugs must pay attention to the pregnancy week, strict control of the dose, duration. Adhere to the rational use of drugs, and discontinue them in a timely manner after the condition is controlled. 5.When two or more drugs have the same or similar efficacy, consider using the drug that is less harmful to the fetus. 6.The use of teratogenic drugs is prohibited. If a pregnant woman is in critical condition, she should consider using them only after carefully weighing the pros and cons. 7.Avoid the combined use of drugs if they can be used alone, and avoid the use of newer drugs if they can be used with more definite conclusions. 8. Prohibit the use of experimental drugs during pregnancy, including pregnancy test drugs. Second, the pregnancy drug consultation specific drugs should be based on the specific actual situation, the evaluation of the impact of drugs on the fetus from two main aspects, one is the type of medication, the second is the time of medication. 1. Time of medication: is it before or during pregnancy? Is it early or mid-late pregnancy? Is it the “all or nothing” period or the sensitive period? Generally speaking, the chance of teratogenicity is small in preconception or “all or nothing” period. During the post-fertilization period, the fertilized egg has not yet been implanted and is not affected by the use of drugs during pregnancy. 8～14 days, just implanted in the endometrium, the fetal layer has not yet differentiated, either spontaneous abortion or no effect. 3～9 weeks, important stage of embryonic development, highly sensitive period of teratogenicity, easily affected by external environment and drugs. After 10 weeks (i.e. after 12 weeks of menopause), the differentiation of organs has been basically completed, and the effect of drugs is minimal, but the fetus may have toxic reactions to drugs. 2, the type of medication, to determine the use of drugs FDA classification: FDA drug classification of pregnant women FDA (U.S. Food and Drug Administration – one of the world’s most stringent drug review agencies) according to the drug has different degrees of teratogenic risk to animals and humans, the pregnancy drugs into five levels: A, B, C, D, X level, for clinical reference to choose the safe use of drugs during pregnancy. Class A: In controlled drug studies, no evidence of fetal harm was seen in women in the first trimester of pregnancy (and no evidence of harm in the subsequent 6 months). The effect of this class of drugs on the fetus is minimal. Common drugs: vitamin C, vitamin D, vitamin E, potassium chloride, levothyroxine sodium, etc. It is important to note that this class of drugs is not a “safe”, and it is still very dangerous to use drugs without medical advice or increasing the dose on your own! Grade B: In animal reproduction studies (no controlled studies on pregnant women), no adverse effects of drugs on the fetus were seen. Or the drug was found to have side effects in animal reproduction studies, but these side effects were not confirmed in women in the first trimester of pregnancy with controls. Common drugs: amoxicillin, ampicillin, cephalosporin antibiotics, erythromycin, azithromycin, metronidazole, clotrimazole, aciclovir, insulin, famotidine. Ibuprofen, but the side effects of the drug in late pregnancy and near delivery are high and should be used with great caution. Paracetamol, an antipyretic and antipyretic ingredient found in many anti-cold medications. Class C: Animal studies have demonstrated that the drug is harmful to the fetus (teratogenic or embryonic death, etc.), or there are no studies in pregnant women with controls, or no studies have been conducted on pregnant women and animals. This class of drugs should be used only after it has been determined that the benefits to the pregnant woman outweigh the risks to the fetus. Common drugs: aspirin, hydrocortisone, gentamicin, nifedipine, theophylline, mycophenolate, ofloxacin, norfloxacin, etc. Class D: There is clear evidence that the drug is harmful to the human fetus. However, despite this, it is absolutely beneficial when administered to pregnant women (e.g. the drug is used to save the life of a pregnant woman or to treat a serious illness that has not worked with other safer drugs). Common drugs: leucovorin, iodine, sulfamethoxazole, carbamazepine, lorazepam, cilazapril, etc. Class X: Drug studies on animals and humans or experience with human medication have shown that the drugs are harmful to the fetus. Also, the application of such drugs is not beneficial to pregnant women and is therefore contraindicated in patients who are pregnant or may become pregnant. Common drugs: Ribavirin (a commonly used antiviral drug), eszopiclone, fluvastatin, lovastatin, paclitaxel, etc.