Neonatal abstinence syndrome most commonly results from in utero exposure to which class of drugs?

• A. It results from in utero exposure to nicotine
• B. It results from in utero exposure to caffeine
• C. It results from in utero exposure to opioids (and sometimes other substances)
• D. It is caused by maternal vitamin deficiency

Answer: (C)

Neonatal abstinence syndrome happens because the fetus becomes physically dependent on opioids during pregnancy. Opioids cross the placenta and stimulate fetal opioid receptors, leading to dependence. After birth, the newborn is no longer exposed to the drug, so withdrawal symptoms emerge as the baby clears the substance from the body. This is most commonly seen with maternal opioid use—whether heroin, methadone, buprenorphine, or other prescription opioids. Other substances can influence or complicate the picture, but opioids are the primary cause. Nicotine, caffeine, or vitamin deficiencies are not the typical culprits for this withdrawal syndrome.