MIDSAGITTAL DIMENSIONS OF THE PRENATAL HUMAN CRANIUM

The purpose of the present study was to analyze the linear dimensions of the cranial base and the anterior facial heights in the median plan e of human fetal crania during the second trimester. The distances mea sured were related to gestational age (GA), crown-rump length (CRL) an d maturation stages of the cranial base (MSS). The material comprised midsagittal tissue blocks of the crania from 52 normal human fetuses a ged 13 to 22 weeks GA with CRL from 78 to 230 mm and cranial base matu ration from MSS 3 to MSS 7. The measurements of the cranial and facial dimensions were performed on radiographs of these tissue blocks. The study confirmed previous observations regarding the dimensional increa se in the linear dimensions of the cranial base and the upper facial h eight in the second trimester. The assessment of absolute changes was further supplemented by an analysis of the percentage changes. This an alysis showed that the percentage changes from MSS 3 to MSS 7 of the l inear dimensions of the cranial base and the upper facial heights were similar. On the other hand, the percentage increase in the lower ante rior facial height during the second trimester was found to be much la rger than that of the cranial base and the upper anterior facial heigh t. It is suggested that this is related to the marked increase of the tooth germs during the period and the concurrent growth of the alveola r processes. Standards for normal prenatal cranial dimensions in relat ion to stages of maturation in the midsagittal cranial base were provi ded. These data may be of value for use in prenatal diagnostics.