The document provides guidance on prescribing medications during pregnancy. It recommends using a small armamentarium of drugs with proven efficacy and minimal side effects. All drugs may affect the fetus, except heparin and insulin. Patients are often exposed to over-the-counter medications in the first trimester, which carries potential risks. The risks of therapy must be weighed against the risks of not treating diseases. Pharmacokinetics in the mother and fetus are affected by physiological changes in pregnancy. Dietary deficiencies can impact fetal growth and development. Supplementation aims to reduce congenital malformations. Past obstetric history including fertility drugs, hormones, and anticoagulants is important. Screening for STDs like HIV is crucial