Ossification of sacral vertebral bodies in neonates born 24 to 38 weeks' gestational age and its relevance to spinal ultrasonography.

ABSTRACT

OBJECTIVE: Determination of gestational age and/or birth weight at which sacral ossification centers appear. STUDY DESIGN: Radiographs were reviewed of newborns admitted to Auckland City Hospital between January 2008 and December 2010. Infants were divided into weight clusters increasing in 100-g increments from 400 g to 3000 g and 500-g increments thereafter, for a total of 29 weight clusters. Adequate images were available for at least five newborns per cluster. RESULTS: Images of 163 newborns were reviewed. All but six newborns had five sacral ossification centers by 32 weeks' gestation and a birth weight of 1800 g. Five of the six infants had a congenital anomaly and associated growth restriction. CONCLUSIONS: Infants can be expected to have all five sacral ossification centers present by the time they reach a gestational age of 32 weeks and/or a birth weight of 1800 g. Variation from this can be associated with congenital anomalies and growth restriction.