Sonographic measurements of the fetal fastigium between 20 and 40 weeks' gestation.

Objective: The purpose of this study was to establish a new reference angle chart for fastigial biometric measurements throughout gestation in normal singleton pregnancies.

Methods: A prospective cohort study was designed. A total of 505 pregnant women between 20 and 40 weeks' gestation were included in the study. Excluded were those with multiple pregnancies, congenital anomalies, abnormal karyotypes, and polyhydramnios or oligohydramnios. Transvaginal or transabdominal sonography was performed in the midsagittal plane of the brain.

Results: The angle of the fastigium was found to be 30 degrees to 60 degrees throughout pregnancy. These data were found to be constant during the progression of pregnancy without any significant changes.

Conclusions: Fastigial measurements throughout pregnancy are presented. Its angle is constant throughout pregnancy. Evaluation of the fastigium may assist in cases of subtle posterior fossa anomalies.