Infants born with neonatal abstinence syndrome (NAS) had significantly smaller head circumference than infants with no fetal exposure to opioids, a researcher said here.
Mean head circumference was almost a full centimeter smaller in infants born with NAS compared to controls (33.04 cm versus 33.99 cm, respectively, P<0.001), reported Craig V. Towers, MD, of the University of Tennessee Medical Center in Knoxville.
At a presentation at the Society for Maternal-Fetal Medicine's Annual Pregnancy Meeting, Towers said that there have only been a few retrospective studies examining the effect of NAS on head circumference, and very limited prospective data on the subject.
He added that recently, a few smaller studies reported smaller brain volumes and abnormal white matter development in older children ages 9 to 14 treated for neonatal abstinence syndrome at birth.
Researchers therefore performed a prospective cohort study, where cases were selected when a neonate ≥34 weeks was diagnosed and treated for neonatal abstinence syndrome in the NICU. This was defined through a Finnegan score (two consecutive scores of ≥10 or one ≥12). Controls were matched for race, parity, mode of delivery and gestational age at delivery, and control mothers did not have illicit substance use based on history and a urine drug screen. All pregnancies were well-dated.
Use of illicit drugs, tobacco, alcohol, gabapentin, anti-emetics and SSRIs were recorded in both cases and controls. Towers noted that the control group had a median of three drug screens, while the cases had a median of six drug screens.
Overall, 858 neonates were assessed -- 429 cases and controls apiece. In addition to the smaller mean head circumference, many more infants with NAS versus controls had head circumference at the 10th percentile or less (30.1% versus 11.9%, respectively, P<0.0001) and the 3rd percentile or less % (8.2% versus 1.9%, respectively, P<0.0001). In line with earlier data, NICU length of stay was significantly longer for infants with neonatal abstinence syndrome compared to controls (about 21 days versus around 3 days, P<0.0001).
In most of the neonatal abstinence syndrome cases, mothers were on opioid agonist medication-assisted treatment, with three-quarters on buprenorphine, and 12% on methadone.
But in a multi-variate analysis, the authors found the only significant risk factor for a smaller head circumference was opioid use in pregnancy resulting in neonatal abstinence syndrome (adjusted OR 3.19, 95% CI 2.23-4.56) -- not any other drug or substance use.
At the presentation, Towers noted that recent guidelines from the American College of Obstetricians and Gynecologists (ACOG) do not recommend detoxification during pregnancy for managing opioid use disorder, and questioned whether this should be revisited.
"Analyses of newborns delivered of mothers that undergo opiate detoxification during pregnancy and deliver newborns without NAS are needed to determine if the current recommended management of [opioid use disorder] in pregnancy should be altered," he said.
Towers said further research is needed to determine if neonates born with neonatal abstinence syndrome are at increased risk for future neurologic dysfunction. He said his group is currently following a cohort of these infants to try to help shed some light on this question.
"Hopefully, I'll be able to come back with follow-up on these kids in 2 to 3 years to tell you how they're doing," he said.