Birth defects, which may be known medically as "congenital abnormalities", are any abnormality in the structure of a baby's body or in the way that their body functions. Birth defects may be genetic, or they may be caused by environmental factors such as drinking alcohol or taking certain medications while pregnant. Sometimes babies are born with birth defects for no known reason, and a significant area of medical research is focused on finding possible causes for some relatively common birth defects. Some babies' birth defects may be obvious when attending for prenatal screening, as they may show on blood tests or on scans of the baby. Some babies' birth defects may be more serious than others. Many are treatable and can be addressed either immediately after birth or sometimes while the baby is still in the womb. Other birth defects may lead to either physical or mental disability, while some may even be fatal.