Neonatal Abstinence Syndrome (NAS) Symptoms & Causes


What causes neonatal abstinence syndrome?

Almost every drug passes from the mother's blood stream through the placenta to the fetus. Illicit substances that cause drug dependence and addiction in the mother also cause the fetus to become addicted. At birth, your baby's dependence on the substance continues. However, since the drug is no longer available, your baby's central nervous system becomes overstimulated causing the symptoms of withdrawal.

Some drugs are more likely to cause NAS than others, but nearly all have some effect on your baby. Opiates, such as heroin and methadone, cause withdrawal in about half of babies exposed prenatally.

  • Cocaine may cause some withdrawal, but the main symptoms in your baby are due to the toxic effects of the drug itself.
  • Other drugs, such as amphetamines, barbiturates and narcotics can also cause withdrawal.
  • Alcohol use causes withdrawal in your baby, as well as a group of problems including birth defects called fetal alcohol syndrome.

Why is neonatal abstinence syndrome a concern?

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.

In addition to the specific difficulties of withdrawal after birth, problems in your baby may include:

Specific drugs often times cause specific problems in your baby:

  • Heroin and other opiates, including methadone, can cause significant withdrawal in your baby, with some symptoms lasting as long as four to six months. Seizures may also occur and are more likely in babies born to methadone users.
  • Prenatal use of amphetamines is associated with low birthweight and premature birth, and may cause intracranial (in the head) bleeding in your baby.
  • A mother's prenatal cocaine use may be related to an increased risk of sudden infant death syndrome (SIDS).
  • Marijuana use is linked to lower birthweight and size of your baby.
  • Alcohol use in pregnancy also has significant effects on the fetus and your baby. The baby's growth during pregnancy and after birth is slowed and she may have deformities of the head and face, heart defects and mental retardation. Withdrawal symptoms from alcohol may last up to 18 months.
  • Cigarette smoking has long been known for its effects on the fetus. Generally, smokers have smaller babies than non-smokers. Babies of smokers may also be at increased risk for premature birth and stillbirth.