Neonatal withdrawal or neonatal abstinence syndrome (NAS) is a withdrawal syndrome of infants after birth caused by in utero exposure to drugs of dependence. There are two types of NAS: prenatal and postnatal. Prenatal NAS is caused by discontinuation of drugs taken by the pregnant mother, while postnatal NAS is caused by discontinuation of drugs directly to the infant. Neonatal withdrawal or neonatal abstinence syndrome (NAS) is a withdrawal syndrome of infants after birth caused by in utero exposure to drugs of dependence. There are two types of NAS: prenatal and postnatal. Prenatal NAS is caused by discontinuation of drugs taken by the pregnant mother, while postnatal NAS is caused by discontinuation of drugs directly to the infant. Some drugs are more likely to cause NAS than others, but nearly all have some effect on the baby. Opiates, such as heroin and methadone, cause withdrawal in over half of babies exposed prenatally. Cocaine may cause some withdrawal, but the main symptoms in the baby are due to the toxic effects of the drug itself. Other drugs, such as amphetamines and barbiturates, can also cause withdrawal. Alcohol use causes withdrawal in the baby, as well as a group of problems including birth defects called fetal alcohol spectrum disorders (FASDs). When a mother uses illicit substances, she places her baby at risk for many problems. A mother using drugs may be less likely to seek prenatal care, which can increase the risks for her and her baby. In addition, women who use drugs are more likely to use more than one drug, which can complicate the treatment. The risk of contracting HIV and AIDS is also greater among intravenous (IV) drug users.