Comparison of Neonatal Abstinence Syndrome Manifestations in Preterm Versus Term Opioid-Exposed Infants

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Twenty percent to 40% of infants exposed to in utero opioid were delivered preterm. There is currently no neonatal abstinence syndrome (NAS) scoring tool known to accurately evaluate preterm opioid-exposed infants. This can lead to difficulties in titrating pharmacotherapy in this population.


To describe NAS symptoms in preterm opioid-exposed infants in comparison with matched full-term controls.


This was a retrospective cohort study from a single tertiary care center of methadone-exposed infants born between 2006 and 2010. Using modified Finnegan scale scores recorded every 3 to 4 hours beginning at 6 hours of life until 24 to 48 hours after medication discontinuation, NAS symptoms was compared between 45 preterm infants and 49 full-term matched controls. Concurrent neonatal medical diagnoses were also compared.


The median gestational age in the preterm group was 35 weeks (interquartile range [IQR] = 33-36) versus 39 weeks (IQR = 38-40) in the term group. Preterm infants scored less frequently for many items including sleep disturbance (24.4% vs 46.2%), tremors (77.9% vs 89.7%), muscle tone (87.9% vs 97.4%), sweating (2.1% vs 9.4%), nasal stuffiness (11.9% vs 20.5%), and loose stools (7.0% vs 14.3%) than full-term controls. Preterm infants scored more frequently for hyperactive moro reflex (26.4% vs 5.5%), tachypnea (19.3% vs 16.1%), and poor feeding (24.6% vs 11.8%).

Implications for Practice:

Provider awareness of differences in manifestations of preterm and term infants with NAS, as well as concurrent prematurity diagnoses that can influence NAS scoring, is needed. These findings mandate the development of a modified NAS scoring tool for the preterm NAS population.

Implications for Research:

A preterm NAS scoring tool needs to be developed and validated to more accurately evaluate and treat preterm opioid-exposed infants.

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