Morphology of the metopic suture during the fetal period.

Assessment of the position and size of the metopic suture and anterior fontanelle is important in the routine examination during fetal period and in newborn infants. The aim of this study is to clarify the average size and its developmental changes of the anterior fontanelle and metopic suture by morphometry. Fifty-one cases were examined over a developmental period ranging from fetus of 14 weeks gestation to full term neonate. The width, and length of heads as well as head circumference of all fetuses were measured. The metopic suture and anterior fontanelle sizes were determined. The nearest distances between the parietal bones to the opposite frontal bones, and the distances between the nasion and lower angle of the anterior fontanelle, bregma and upper angle of the anterior fontanelle were measured. The averages of longitudinal and transverse diameters and areas of anterior fontanelle were calculated. Significant correlation was found between all the parameters and gestational ages, and between the sizes of the metopic suture and of skulls. There was no difference between male and female in any of the parameters. In our study, closed metopic suture was not observed. The anterior fontanelle is easy to palpate, and its enlargement might occasionally be helpful in the clinical examination of the newborn infants. The presence of a wide metopic suture may indicate the possibility of additional defects and anomaly in the newborn.