Inaccuracy of Ballard scores before 28 weeks' gestation. National Institute of Child Health and Human Development Neonatal Research Network.

OBJECTIVE: Ballard scores are commonly used to estimate gestational age (GA). The purpose of this study was to determine the accuracy of the New Ballard Score (NBS) for infants <28 weeks GA by accurate menstrual history and to evaluate NBS as an outcome predictor.
METHODS: Infants weighing 401 to 1500 g in 12 National Institute of Child Health and Human Development Neonatal Research Network centers had NBS performed before age 48 hours. Accuracy of NBS estimates of GA was assessed for infants with GA determined by accurate menstrual history. In a larger cohort of infants, NBS was included in regression models of the association of NBS and death, poor outcome, and duration of hospital stay.
RESULTS: At each week from 22 to 28 weeks GA by accurate menstrual history, NBS estimates exceeded GA by dates by 1.3 to 3.3 weeks, and estimates varied widely (range of widths of 95% CIs for the observations, 6.8 to 11.9 weeks). NBS did not contribute significantly to regression models of death, poor outcome, or duration of hospital stay.
CONCLUSIONS: Inaccuracies in GA determined by the NBS should be considered when treating extremely premature infants, particularly in decisions to forego or administer intensive care. Refinement of GA scoring systems is needed to optimize clinical benefit.