Pregnancy Exposures
Teratogen refers to any agent that causes a structural abnormality following fetal exposure during pregnancy. Teratogens may include: infectious agents (rubella, cytomegalovirus, varicella, herpes simplex, toxoplasma, syphilis, etc.); physical agents (ionizing agents, hyperthermia); maternal health factors (diabetes, maternal PKU); environmental chemicals (organic mercury compounds, polychlorinated biphenyl or PCB, herbicides and industrial solvents); and drugs (prescription, over- the-counter, recreational). The dose and the time of exposure to a particular agent often determines whether or not the baby will be adversely affected and to what degree. In general, the first trimester is a more vulnerable time for the fetus than the second and third trimesters.
Medications are typically classified in several categories depending on their effects on pregnancy. Category A medications, such as prenatal vitamins, have been proven to be safe during pregnancy with well controlled human studies and do not increase the risk of adverse pregnancy outcomes or birth defects. Category B medications, such as acetaminophen, have not been shown to substantially increase the risk of adverse pregnancy outcomes or birth defects, but well controlled human studies may not be available or are inconclusive. Category C medications, such as Cymbalta, have indicated some adverse fetal effects in animal studies but limited or no human data is available. Category D medications, such as aspirin, have some evidence indicating there may be an increased risk in humans, but may be a quite necessary drugs to use and the benefits may outweigh the risks of the drugs. Category X medications, such as Isotretinoin (an acne medication), are known to cause adverse fetal effects and are considered unnecessary medications during pregnancy and should be avoided.
Please contact one of our available practices, the Center for Prenatal Diagnosis or the Maternal Fetal Medicine and Genetics Center for more information, or you may wish to consult the following resources:
