Commonly used antirheumatic drugs: NSAIDs, glucocorticoids, hydroxychloroquine (HCQ), methotrexate (MTX) leflunomide (LEF), cyclophosphamide (CTX), mycophenolate mofetil (MMF), azathioprine (AZA), cyclosporine (CsA), salbutamol (SSZ), thalidomide, biologics (TNFi). The U.S. Food and Drug Administration (FDA) classifies drugs into five categories, A, B, C, D, and X, based on animal studies and clinical experience with the effects related to fetal teratogenicity. Category A: Drugs used in the first trimester of pregnancy have not been found to cause fetal harm by clinical control observations, nor have they been found to cause fetal harm during subsequent pregnancies. Category B: Animal reproduction experiments have not shown harm to the fetus, but there is a lack of clinical control observation data, or harm to the fetus has been observed in animal reproduction experiments but has not been confirmed in clinical trials in early pregnancy. C: Side effects on the fetus (teratogenic or embryonic lethal or otherwise) have been confirmed in studies in animals, but no control group is available in women or no information is available in studies in women and animals. Drugs only when weighed against the benefits to the fetus outweigh the harms D: positive evidence of risk to the human fetus, but despite the harms, the benefits to the pregnant woman need to be confirmed before application (e.g., safer drugs cannot be applied for life-threatening or serious illnesses or drugs are ineffective), such as tetracyclines, phenytoin sodium, chlorosulfonylurea, etc. X: Has been shown in animal or human studies to cause fetal abnormalities or is known to be dangerous to the fetus based on human experience, harmful to humans or to both, and the application of the drug to pregnant women clearly outweighs any beneficial effects. This drug is contraindicated in women who are pregnant or who are about to become pregnant. For example, hexestrol, thalidomide, ribavirin, etc. The use of antirheumatic drugs in women before and during pregnancy Hormones available during pregnancy (Level C) Some prospective studies suggest that hormone doses >15 mg/d increase the risk of intrauterine infection and preterm delivery, while doses <7.5 mg/d also increase the risk of preterm delivery, so the lowest dose of hormones is recommended. The use of hormones in early pregnancy increases the risk of neonatal cleft lip and should be used with caution. Prednisone or prednisolone is mostly metabolized to inactive metabolites by placental 11β-hydroxysteroid dehydrogenase after use and should be preferred. NSAIDs are used differently in different pregnancy periods NSAIDs (class B) can be used in small doses and intermittently in early pregnancy: it will not increase the risk of fetal malformation, but it will interfere with fertilized egg implantation and placental circulation, luteinization unruptured follicle syndrome, and increase the risk of abortion. NSAID (Class C): COX-1 and COX-2 are expressed in endothelial cells and smooth muscle cells of arterial ducts and in renal tissues, which can cause arterial stenosis or premature closure and pulmonary hypertension, fetal renal impairment, decreased urine output and low amniotic fluid. Hydroxychloroquine (Class C) is tolerated during pregnancy and can be used in small doses during pregnancy to prevent malaria without increasing the risk of fetal congenital anomalies or miscarriage. One study showed no increase in genetic abnormalities or visual or auditory impairment in 250 SLE patients with HCQ during pregnancy. Low-dose SSZ (2g/d) does not affect female fertility and does not increase the risk of fetal anomalies. However, SSZ inhibits folic acid synthesis and has an increased risk of neural tube defects, cleft lip and cardiovascular defects, and folic acid supplementation when used may reduce the risk of cleft lip. Azathioprine (Class D) is available during pregnancy Although azathioprine can cross the placenta, the fetal liver lacks inosinate pyrophosphorylase and azathioprine cannot be activated, reducing the toxicity to the fetus, and can be used throughout pregnancy. However, the dose needs to be ≤2 mg/kg, otherwise it increases the risk of hematopoietic suppression in infants and children. The author has encountered 2 cases of lupus nephritis patients with normal delivery after using CsA during pregnancy, and the fetuses were not abnormal. Methotrexate (Class X) Methotrexate (MTX) is a folic acid antagonist and its use in early pregnancy can cause methotrexate syndrome. Leflunomide (Class X) is contraindicated during pregnancy. Thalidomide (Class X) is contraindicated during pregnancy. The most dangerous period for the use of thalidomide is 3-8 weeks of gestation, and serious adverse effects can occur with 2-3 doses of 50 mg or 25 mg/day, even with 1 dose. The use of biological agents during pregnancy is controversial Most biological agents contain lgG-Fc. lgG-Fc selectively passes through the placenta in a time-dependent manner and rarely passes in early pregnancy (first 3 months), gradually increasing from 12 weeks of pregnancy and increasing in the fetus at 36-40 weeks of pregnancy, exceeding the maternal dose. Therefore, biological agents are available in early pregnancy. The use of TNF inhibitors (etanercept, infliximab, adalimumab, etc.) during pregnancy is in risk class B. TNF inhibitors can be applied before pregnancy to improve the condition. Human trials have shown minimal crossing of the placenta in early pregnancy, and no teratogenicity or other adverse effects have been found. However, the long-term effects on children are unclear, so discontinuation is not necessary during the months of attempted pregnancy and should be discontinued as soon as possible after pregnancy is discovered. The use of biologics requires individualized assessment of the risk-to-benefit ratio of the drug and careful use, and caution should be exercised until more reliable research data are available.