Learning Objective #1: The learner will be able to identify knowledge gap in estimating gestational age (GA) using standard New Ballard Examination (sNBE) in newborns including preterm infants.

Learning Objective #2: The learner will be able to understand the validity of the extended NBS (eNBE) for GA estimation to newborn population including preterm infants.

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Purpose: The disadvantage of sNBE is the 5-point intervals for total scores, and 2-week intervals for GA. This limitation leads to maximum variations of 5 points or 2 weeks in GA assessment, which may be not trivial, especially for pretern newborns. An explorative study was performed to examine the accuracy of the extended New Ballard Examination (eNBE) in gestational age (GA) estimation of Korean newborns, including preterm newborns.

Method: The eNBS scoring system was extended to include all numbers of total score of NBS and GA to allow a 3-days variation in GA estimation compared to the original scale which has a 2-week variation due to the application of a 5-score interval for the total NBS score and only even numbers for GA. GA by eNBS(GA-eNBS) was compared with GA by LMP(GA-LMP) and GA by standard NBS(GA-sNBS) in 213 Korean newborns including preterm newborns. Difference between GA-LMP and GA-eNBS was analyzed for each GA.

Results: The results suggested that the eNBE was functionally identical to the sNBE, with a high correlation (r = .985 versus .998) and almost same Euclidean distance (88.414 versus 86.428). Overestimation of GA up to 1 week by the eNBE was observed in preterm infants, while underestimating up to 1 week in postterm newborns.

Conclusions: The accuracy of the extended NBE was validated with 3 days of variation in GA estimation, but 2 weeks in the standard NBE. Overestimation of GA by NBE may occur in premature infants because of fetal acceleration to stress, such as preterm birth, or ethnic variation, while underestimation, of the deceleration of fetal maturity in postterm newborns.