Statistical characteristics of anterior fontanelle size at birth of term Sri Lankan new borns: a descriptive cross sectional study.

INTRODUCTION Assessing the anterior fontanelle size is an important component of routine neonatal examination. For meaningful interpretation of fontanelle size, normal reference values are essential. Normal values for the fontanelle size in Sri Lankan newborns are not available. OBJECTIVES To investigate characteristics of anterior fontanelle size at birth in Sri Lankan babies. METHODS A descriptive cross sectional study was carried out between October and November 2010. Horizontal and vertical dimensions of the anterior fontanelle were measured in 2215 normal term babies, between 12 to 24 hours after birth. A practical and simple method was used to measure fontanelle size. Average fontanelle size was calculated by adding horizontal and vertical dimensions and dividing by two. RESULTS Mean of the average fontanelle size for the total sample was 2.55 cm (for males 2.57 cm and for females 2.52 cm). Longitudinal dimension was significantly higher than the horizontal in both sexes (p<0.001). Frequency distribution curves of fontanelle size followed a normal distribution in both sexes. The ninety seventh centile and third centile for the average fontanelle size were 4.5 cm and 0.9 cm respectively. CONCLUSIONS Babies with an average anterior fontanelle size more than 4.5 cm or less than 0.9 cm need further follow up. Further studies are needed to evaluate the accuracy of these cut off values.