Pons Anteroposterior and Cerebellar Vermis Craniocaudal Diameters in Fetuses With Down Syndrome.

Abstract

To investigate the pons anteroposterior diameter (APD) and cerebellar vermis craniocaudal diameter (CCD) of fetuses with Down syndrome (DS). This was a prospective observational study including 200 low-risk pregnancies and 18 pregnancies with fetuses who had DS. A midsagittal view was obtained to measure the pons APD and cerebellar vermis CCD. Gestational age-related 5th, mean, and 95th percentiles for the pons APD and cerebellar vermis CCD between 18 and 32 weeks' gestation were created from the low-risk population. Each measurement of a fetus with DS was plotted on growth charts, and those below the 5th percentile for gestational age were considered small. The pons APD and cerebellar vermis CCD measurements were below the 5th percentile for gestational age in 7 of the 18 (38.8%) fetuses with DS. Fetuses who had pons APDs below the 5th percentile for gestational age also had cerebellar vermis CCDs below the 5th percentile. Fetuses who had pons and cerebellar vermis measurements below the 5th percentile for gestational age on the initial examination continued to have small measurements during follow-up. Fetal pons and cerebellar vermis abnormalities could be observed prenatally in fetuses with DS, which could help in the antenatal counseling and postnatal follow-up of such pregnancies.