During pregnancy, the liver’s biotransformation function decreases, which, combined with elevated estrogen levels and biliary pooling, can easily produce drug toxicity and endanger the fetus. The FDA (U.S. Food and Drug Administration) classifies drugs used during pregnancy into five categories. Category A is the safest category as no damage to the fetus has been observed in animal experiments and clinical observations. Category B is the safest category because animal experiments have shown that it is harmful to the fetus, but clinical studies have failed to confirm. Or animal experiments did not find any teratogenic effect. But there is no clinical data to verify. Category C is the one with teratogenic or embryonic killing effect on fetus only confirmed in animal experiments, but there is no research data to confirm in human. Class D is a class of drugs that have been clinically proven to have harmful effects on the fetus but with definite efficacy. If a pregnant woman is seriously ill or threatened with death and there is no alternative drug, it can be considered but should be applied with caution. Class X is a drug that has been proven to be harmful to the fetus and is prohibited. Such as thalidomide. I. Dermatitis, eczema Topical Furamyl lotion, Benadryl cream for pregnant women and fetuses generally do not have any side effects. Commonly used topical hormone ointments, all FDA category C, have potential side effects for topical use (cleft lip, palate), but there is a lack of sufficient clinical evidence. They can be used in appropriate amounts depending on the condition, such as weakly acting hormones. The calcium phosphatase inhibitors Tacrolimus and Pimecrolimus belong to Class C. Tacrolimus is not recommended because it can pass through the placenta when taken orally, causing hyperkalemia and renal dysfunction in newborns and can be excreted in breast milk. The study proves that pimecrolimus cream can be used topically, but lactating women should avoid using it on the breast area to avoid absorption by the infant. Anti-allergic drugs H1 Cyproheptadine, Chlorpheniramine, Benadryl, Cetirizine, Loratadine, Mizolastine, are all Class B drugs and should not be given to pregnant women in the early stages of pregnancy (3 months). Among them, chlorpheniramine and cyproheptadine are safer and paracetamol is the safest. H2 Cimetidine (Class C). III. Acne Acne during pregnancy is mainly topical topical medication. Erythromycin (class B drug), clindamycin (class B drug), metronidazole (class B drug) and azelaic acid (class B drug) are. Benzoyl peroxide (Class C drug) . Tetracyclines (D) IV. Bacterial infections Penicillins and cephalosporins in addition to the possible allergy of pregnant women. When used during pregnancy, the effect on the fetus is minimal. Low toxicity． High safety. They can be used for all stages of pregnancy infection. The most safe are penicillin and cephalosporin. Metronidazole is a drug for the treatment of trichomoniasis, but it is also an excellent drug for the treatment of anaerobic bacterial infections. It has been confirmed in a large amount of clinical data accumulated over a long period of time that although applied in early pregnancy, metronidazole does not increase the teratogenicity of the fetus. V. Fungal infections Miconazole, clotrimazole and myclobutanil can be used as topical vaginal medications during pregnancy. Terbinafine (class B drug) either orally or topically. In fetal toxicity and fertility animal studies have shown no adverse effects. However, it has not been studied in controlled trials in pregnant women. Grayfloxacin (class B drug) has been reported to cause conjoined twins, abnormalities in the nervous system and skeletal system of offspring in animal studies Fluconazole and Itraconazole are both class C drugs.