Morphometry of the second trimester fetal brain. Comparison of ultrasonographic and post-mortem findings.

With the increasing use of ultrasound examination in the antenatal period the lack of morphological correlates has become a problem. This study was carried out in order to correct this deficiency. An antenatal real-time ultrasound scan of the fetal head was performed and measurements of the biparietal diameter, occipitofrontal diameter, head circumference and cerebral ventricle-to-hemisphere ratio were undertaken in 103 fetuses at 13-24 weeks gestation. After prostaglandin termination of pregnancy, the fetal brains were perfused in situ through the right carotid artery with 10% formal saline. Horizontal slices of the fetal head were cut, photographs were obtained and measurements of the same parameters as in the ultrasound examination were undertaken. There is a significant correlation (p less than 0.001) between the ultrasonographic and post-mortem measurements of all parameters. Also several anatomical structures of the fetal brain are now confidently identified in the antenatal ultrasound scan, using the anatomical preparations for comparison.