In my clinical practice, I often encounter maternal colds, fevers, and situations that require antibiotics. Below I analyze the latest FDA grading criteria for maternal medications in the hope that it will help you. The FDA classifies drugs into 5 levels of harm to the fetus: A, B, C, D, and X, based on their teratogenicity to the fetus: Class A: proven to be harmless to the fetus in human studies with control groups. This includes multivitamins, vitamin preparations during pregnancy, but not high-dose vitamin preparations. Class B: proven harmless to fetuses in animal experiments, but no studies in humans yet; or animal experiments proved to have adverse effects, but this effect was not found in studies with good control groups in humans. 1, antibiotics: ① penicillins: for class B drugs, low toxicity, is the safest anti-infective drugs for pregnant women, including broad-spectrum penicillin such as ampicillin, piperacillin, meloxicillin and other β-lactam preparations. ②, Cephalosporins: Class B drugs. These drugs can pass through the placenta, but there are no reports of teratogenicity of such drugs, and the plasma half-life is shorter in pregnancy than in non-pregnancy. They are available during pregnancy. (3) Macrolides: mostly class B. Because of their large molecular weight, they do not easily pass through the placenta. It can be used for penicillin allergy and chlamydia and mycoplasma infection. ④Jessamycin: including jessamycin and clindamycin, etc., which are class B drugs. It can pass through the placenta and enter the breast milk, and has no record of adverse effects on the embryo, so it is relatively safe. ⑤ Metronidazole: Now it is class B, and it was classified as class C in the past. It has been reported that 1700 cases of early pregnancy did not increase the rate of malformation after application, and recently the FDA has classified it as a Class B drug. The CDC has recommended it for the treatment of vaginal trichomoniasis during pregnancy. However, tinidazole is a class C drug and should be used with caution during pregnancy. Ornidazole: No teratogenicity in animal studies, but no controlled studies in pregnant women, so use with caution. 2. Antiviral drugs: ①Viriconazole: triazolyl nucleoside, a class X drug, was found to be teratogenic and embryonicidal in almost all species of animals tested in animal experiments, and is prohibited during pregnancy. The elimination of this product in the body is very slow, four weeks after the drug can not be completely removed from the body. 3, antifungal drugs: mycoplasma and clotrimazole, both Class B drugs, available during pregnancy; the rest of the antibacterial drugs are prohibited or used with caution.