Which of the following is NOT a sign of Neonatal Abstinence Syndrome (NAS)?

Improved sleep patterns is indeed not a sign of Neonatal Abstinence Syndrome (NAS). NAS occurs in newborns who have been exposed to certain substances, such as opioids, in utero. The signs of NAS generally arise from the infant's withdrawal from substances and reflect central nervous system irritability and dysfunction.

Hypertonia, irritability, and poor feeding are common symptoms associated with NAS. Hypertonia refers to increased muscle tone, which can make the infant appear stiff or difficult to handle. Irritability is a hallmark of NAS; affected infants often exhibit excessive crying and restlessness due to withdrawal symptoms. Poor feeding is also a characteristic sign, as infants may have difficulty coordinating sucking and swallowing or display a decreased interest in feeding.

In contrast, improved sleep patterns would be atypical for an infant experiencing withdrawal. Instead of sleeping better, these infants typically show fragmented sleep, making the presence of improved sleep patterns an unlikely indicator of NAS.