Ultrasound evaluation of the fetal skull base throughout pregnancy.

Abstract

To construct nomograms for cranial base parameters of normal fetuses. A cross-sectional study of 386 normal singleton fetuses at 14-40 weeks' gestation. Measurements of the length and width of the sphenoid bone anteriorly and the otic cartilage posteriorly and of the angles between the ridges were obtained. Nomograms of the length and width of sphenoid ridge and otic cartilage, and of the angles in the cranial fossae are presented. A linear growth function was observed between cranial base measurements (sphenoid ridge length, otic cartilage length, cranial base angles) and gestational age, femur length and biparietal diameter. Measurements of the length of cranial base ridges and the angles between them can be obtained easily in the second and third trimesters and might prove useful in the evaluation of pregnancies at high risk for associated fetal abnormalities.