As you can see from my blog post of July 27th of this year, we know genetics influences the risk of developing opioid addiction. Now, according to a 2013 study, we know that certain genes are associated with less severe neonatal abstinence syndrome. 
Neonatal abstinence syndrome, called NAS, occurs in about 50% of babies born to mothers maintained on methadone or buprenorphine. Of course, NAS also occurs in babies born to mothers using other opioids, prescribed or illicit, but this study only included mothers in addiction treatment on methadone or buprenorphine.
The withdrawal signs seen in infants are gastrointestinal: diarrhea, poor feeding, and vomiting; central nervous system: tremor, increased muscle tone, increased startle response, and poor sleep; and other symptoms like sneezing, yawning, increased respiratory rate, fever, sweating, and nasal stuffiness. For infants, NAS is a serious medical problem that can cause seizures and even death if untreated, so it is important for doctors to know if an infant has been exposed to any opioids during the pregnancy. With longer-acting opioids like buprenorphine and methadone, the withdrawal can be delayed for up to a week. With short-acting opioids like heroin, withdrawal can occur quickly in the infant.
Thankfully, NAS is treatable, and most hospitals use a standardized protocol to check babies for serious withdrawal signs. If the baby has more than mild signs, an infant-sized dose of opioid is administered in tapering doses, to gradually reduce physical withdrawal.
Aside from treating the baby with tapering doses of opioid medication, we know other things can help reduce the severity of NAS. Reducing or even better quitting smoking before or during pregnancy reduces the chances of neonatal withdrawal, as can breastfeeding. Contrary to popular belief, it isn’t methadone or buprenorphine in the breast milk that helps withdrawal; it’s the warmth and comfort of being at the mother’s breast that soothes the baby. Similarly, babies are calmed when their environment is quiet and dark, and swaddling (wrapping the baby closely in a blanket) also helps.
Most people assume that the higher the mom’s dose of methadone or buprenorphine, the more likely it the infant will have withdrawal, but repeated studies show no clear relationship between maternal dose and the likelihood of NAS.
But now, this study shows we may become able to predict which babies will have more severe withdrawal based on genetic profile.
This prospective cohort study, conducted in Maine and Massachusetts from July 2011 to July 2012, looked at eighty-six pairs of mothers and infants. The study looked at length of hospital stay for the infants and the need for medical treatment for NAS in those infants. The study found that babies with certain genetic variants of the OPRM1 gene and the COMT gene had significantly shorter hospital stays and needed significantly less medication to treat withdrawal symptoms.
Of course, we can’t change genetic makeup, but we may be able to use this information someday to help predict which babies need longer hospital stays and more medication for their NAS. Ultimately, these studies may help us better understand NAS and how to treat it.
With the recent increase in incidence of opioid addiction, more women are getting pregnant while addicted to opioids. Most hospitals have seen an increase in the percentage of babies born with NAS, so this is an important area of research.
1. Wachman et al, “Association of OPRM1 and COMT Single-Nucleotide Polymorphisms With Hospital Length of Stay and Treatment of Neonatal Abstinence Syndrome.” Journal of the American Medical Association, May 1, 2013, Vol. 309(17).