Fontanelle sizes in term neonates in Ibadan, Nigeria

Fontanelle sizes were studied in 200 term and appropriate-for-gestational age neonates delivered at the University College Hospital, Ibadan, Nigeria with the aim of determining their normal range of variation. The anterior and posterior fontanelle sizes were described using the range, mean, standard deviation and selected (3rd, 25th, 50th, 75th and 97th) percentiles. The anterior fontanelle size ranged from 1.0 to 6.4 cm with a mean of 4.0 (SD 1.0) cm. The posterior fontanelle size ranged from 0.0 to 5.5 cm with a mean of 1.4 (SD 1.7) cm. The posterior fontanelle was not palpable in 99 (49.5%) of the neonates and there was no association between the sex of the neonate and posterior fontanelle closure (X2 = 0.97, p = 0.325). The findings of the study are consistent with those of other workers who have documented larger anterior fontanelle sizes in the Negro neonate compared to his caucasian counterpart. However, the anterior fontanelle size in this study was larger than previously reported Nigerian figures, a fact which may be due to the exclusion of neonates who still had overriding cranial bones (from excessive moulding) at the time the measurements were taken. It is suggested that local values derived from well-defined populations be used as reference in the evaluation of the child with dysmorphic features in order to avoid errors of classification due to racial differences in the normal range of variation. Further studies of this nature are needed in order to delineate such differences where they exist.