To assess the effect of examination time on newborn neurobehavioral examinations administered within 48 hours of delivery and to identify the earliest appropriate time for performing the assessment.
We analyzed data from neurobehavioral examinations on 324 newborns using the NICU Network Neurobehavioral Scale (NNNS). Trends over examination time and cumulative percentage within published normal ranges were analyzed to identify the earliest appropriate time for administering the examination. Ordinal logistic regression and multivariate regression were used for testing and defining the earliest appropriate time for administering the examination without being influenced by acute effects of labor and delivery while controlling for several potential confounding factors.
The arousal, excitability, lethargy, quality-of-movement, hypotonicity, and nonoptimal-reflexes scales were sensitive to timing of the examination. Results of ordinal logistic regression showed that 20 hours after delivery seemed to be the earliest appropriate time for administering newborn NNNS examinations. The proportion of NNNS scores within the normal range increased with time significantly when the examination was made less than 20 hours after delivery (n = 148) (odds ratio: 1.12 [95% confidence interval: 1.02–1.23]), but there was no longer significant association with time of examination after 20 hours (n = 176) (odds ratio: 1.04 [95% confidence interval: 0.99–1.09]). This result was confirmed by multivariate regression.
We recommend 20 hours after delivery as the earliest appropriate time for administering newborn NNNS examinations to obtain results reflecting outcomes that are a representative assessment of newborn neurobehavior and not contaminated by acute effects of labor and delivery.