Study: NAS linked to smaller head circumference at birth
MelissaJenco, News Content Editor
Infants with neonatal abstinence syndrome (NAS) often were born with smaller head
circumference compared to newborns who were not exposed to opioids, a new study found.
Researchers from the University of Tennessee Medical Center studied 429 infants born
between April 1, 2014, and Dec. 31, 2016, who were delivered at 34 weeks’ gestation
or later and were treated for NAS. About 87% of the mothers were on opioid medication-assisted
treatment, which is recommended by the American College of Obstetricians and Gynecologists.
The team matched these infants to infants who had not been exposed to opioids using
race, mode of delivery, gestational age and parity. It found the NAS group had a mean
head circumference that was 9.5 millimeters less than controls, according to “Neonatal
Head Circumference in Newborns with Neonatal Abstinence Syndrome” (Towers CV, et al.
Pediatrics. Dec. 10, 2018, https://doi.org/10.1542/peds.2018-0541).
About 30% of infants with NAS had a head circumference in the 10th percentile or lower
compared to 12% of controls. About 8% were in the third percentile or lower compared
to 2% of controls. Reductions in birth weight were smaller than reductions in head
When plotting the data to create Gaussian curves, researchers found a shift to the
left indicating head circumference may have been affected even for those who fell
into the normal range.
They also found that while infants with NAS often were exposed to other substances,
only the opioids put them at significant risk of having small heads.
“Because newborn HC (head circumference) is an indirect measure of brain volume, further
research is necessary to determine if this finding increases the risk for long-term
neurodevelopmental delay,” authors wrote.
They also called for more research on the effects of detoxing during pregnancy and
outcomes of infants exposed to opioids who do not develop NAS.