Sternal ossification in normal newborn infants.

The lateral chest radiographs of 200 Nigerian newborn infants, whose gestational age was estimated by the Dubowitz examination, were analysed for the pattern of ossification of sternal segments. The length of each visible centre was also measured. The manubrium was ossified in all infants over 35 weeks. All infants 37 weeks and above demonstrated ossification of the first and second mesosternal segments. Ten infants had ossification of the xiphisternum. The average number of ossified segments seen in this study is more than previously reported amongst Caucasian infants. The length of each segment correlated better with birth weight than gestational age. Our findings indicate that any infant with two ossified sternal segments, including the manubrium, is at least 30 weeks and those with 3 and 4 segments 34 and 37 weeks gestation, respectively. There is no difference in the pattern of sternal ossification between the sexes.