NAS (neonatal abstinence syndrome) is caused by opioid-dependence during pregnancy. Researchers at Tufts Medical Center recently revealed a connection between genetic variants in newborns with the condition, length of hospital stay and necessary treatment. The link may be useful for doctors treating infants with NAS.

As is the case with all medical conditions, the underlying mechanisms that cause and affect the condition are the cornerstone of research, diagnosis, and treatment. In the case of infants with NAS, the underlying mechanisms may be associated with genetic changes caused by opioid dependence.

The use of opioid drugs during pregnancy has increased in the last 10 years. Approximately 6 in 1,000 infants are born to mothers taking opioid drugs every year. NAS, a condition associated with opioid use during pregnancy, affects the gastrointestinal tract, nervous system, and respiratory system. The effects are associated with drug use, but also with side effects from drugs used to curb opioid dependence during pregnancy. The number of infants affected by NAS has tripled with up to 80% of infants born to mothers taking buprenorphine or methadone. Previous studies have revealed clinical factors associated with the condition, like smoking during pregnancy and taking psychiatric prescription medications, but researchers believe this is the first study to reveal genetic factors at play.

Genes thought to be affected by NAS include ABCB1, OPRM1, and COMT. Researchers evaluated 86 mother/infant pairs for the study. Only infants born on or after the 36th week of gestation were included and all mothers were given buprenorphine or methadone during pregnancy. Infants born to mothers taking opioid treatment during pregnancy were kept in the hospital, on average, about nine days longer than the group average. NAS affected 65% of infants in the study.

When genetic variances were evaluated, researchers found a connection between OPRM1, COMT, and length of hospital stay. Infants falling into these two genetic groups stayed fewer days in the hospital and required less treatment and, in some cases, no treatment for opioid withdrawal. Infants in the ABCB1 group were not protected from longer hospital stays or treatment.

The research gives doctors a look inside how opioid dependence affects infant genetics, but clinical testing is not complete. “To our knowledge, this is the first study to examine the association of genomics with opioid withdrawal in infants and may provide insight into the mechanisms underlying NAS. There is a need for replication of these results before a more definitive conclusion can be made of the association between OPRM1 and COMT variants and NAS.”

Source: Elisha M. Wachman, MD; Marie J. Hayes, Ph.D.; Mark S. Brown, MD, MSPH; Jonathan Paul, Ph.D.; Karen Harvey-Wilkes, MD; Norma Terrin, Ph.D.; Gordon S. Huggins, MD; Jacob V. Aranda, MD, Ph.D.; Jonathan M. Davis, MD. Association of OPRM1 and COMT Single-Nucleotide Polymorphisms With Hospital Length of Stay and Treatment of Neonatal Abstinence Syndrome. JAMA. 2013;309(17):1821-1827. doi:10.1001/jama.2013.3411.