Although all local anesthetics cross the placenta, when administered properly and in the correct amounts, the administration is relatively safe. Lidocaine and prilocaine are category B drugs, while mepivicaine and bupivicaine are in category C. However, prilocaine is an ester and has been associated with methhemoglobinemia induced maternal and fetal hypoxia. Articaine is a category C drug due to limited studies of its safety in pregnancy. Mepivicaine and bupivicaine are category C drugs that can cause fetal bradycardia. Epinephrine is also in category C. Intravascular injection during administration of a local anesthesia with epinephrine may theoretically cause insufficiency of uteroplacental blood flow. However for the healthy pregnant patient, the 1:100,000 epinephrine concentration used in dentistry, using proper aspiration technique and minimal dosing should be safe.