What is safe and what is dangerous to use drugs during pregnancy, let’s first understand the “all or nothing” benefit, which refers to the effect of drugs on the embryo within 2 weeks from the start of fertilization: either it leads to the miscarriage of the child, or it does not affect anything and there is nothing wrong with the child. Fertilization usually occurs in the middle of menstruation, if the menstruation is once in 28 days, then the full or no benefit is probably within a month of menstruation, if the drug is taken without knowing the pregnancy, there is no need to be too nervous, if the child survives, then there is usually no problem. Then, after 2 weeks, whether the drug has an effect on the child, we will probably need to know the U.S. Food and Drug Administration (FDA) classification of drugs for gestational age. To state whether a drug has an effect on the embryo, one needs to look at its results on animal tests and human studies. the FDA classifies all drugs into several categories A/B/C/D/X. Category A: Controlled studies have found no risk to the human fetus in early pregnancy (and no evidence of risk in mid to late gestation), and the potential for fetal damage looks small. Category B: Animal reproduction studies did not find a risk to the fetus, when there were no results from controlled studies in human pregnant women; or animal reproduction studies showed adverse effects (not just reduced fertility) but were not confirmed in controlled studies in human women in early pregnancy (and no evidence of risk in mid- to late-pregnancy). Category C: Animal studies showing adverse effects on the fetus (teratogenic or embryonic killing effects, etc.) but no controlled studies in human women or no information from human and animal studies, and the drug should be used only if the potential fetal benefit outweighs the potential risk. Category D: There is definite evidence of risk to the human fetus, but these risks are acceptable for the benefit of the pregnant woman (e.g., the drug is used in a life-threatening situation, or the condition is too severe to use a safe drug or a safe drug is ineffective) Category X: Animal or human studies show the presence of fetal malformations, or human experience shows risk to the fetus or both, in pregnant women The risks of using the drug clearly outweigh any possible benefits. The drug is contraindicated in women who are pregnant or who may become pregnant. Almost any drug can be searched for its FDA classification, and once we know its classification, we can answer the patient’s question. For example, a friend told me that she had irregular periods and found out she was pregnant at 40 days of menopause and was taking furadantin tablets for a urinary tract infection at about 35 days. Because of irregular periods, you can use ultrasound to determine the week of pregnancy if the actual week of pregnancy is less than 4 weeks (we calculate the week of pregnancy from the last menstrual period). Similarly, for patients with pre-pregnancy comorbidities, such as hyperthyroidism, is it necessary to continue the medication during pregnancy? However, if the hyperthyroidism is uncontrolled and the effects of the disease on the mother and child outweigh the effects of the medication on the child, then it is necessary to consider continuing the medication during the pregnancy (EQJ’s opinion: generally consider using methimazole after 3 months) to control the hyperthyroidism, unless the hyperthyroidism has been controlled. The above mentioned medications should be considered on top of the above. If the drug is excreted quickly in the body, it is not a big problem, but if it takes a long time to be excreted after taking the drug and may have an effect on the child, then care needs to be taken. For example, the half-life of ribavirin (virazole) is 12 days, and it takes a long time to metabolize the drug after a single dose, so when there is residual drug in the body, it is not possible, and the FDA recommends that pregnancy be considered 6 months after the drug is stopped. There is no strictly designed clinical trial results for Chinese medicines or proprietary Chinese medicines, so the effect on the embryo cannot be evaluated using the FDA classification criteria, which is a lack. It may be helpful to read the medication instructions or consult with an herbalist.