Fetal transverse cerebellar diameter in different ethnic groups

Aims: Transverse cerebellar diameter has been described as a tool to check for gestational age, but there are no available studies that attempt to det ermine differences in transverse cerebellar diameter between groups of diff erent ethnic origin. The present study was undertaken to check for differen ces in ultrasound-measured transverse cerebellar diameter between pregnant women of autochthonous Belgian origin and migrant women from Morocco and Tu rkey. Methods: A prospective cross-sectional study was performed. Patients were p regnant women presenting between 17 and 40 weeks of gestational age. Only u ncomplicated singleton pregnancies with a known date of the last menstrual period confirmed by first trimester ultrasound were included. The father of the child had to be of the same ethnic origin as the mother. Polynomial re gression was fitted for the three different ethnic groups. Results: The transverse cerebellar diameter was obtained in 471 singleton f etuses, including 333 Belgian, 69 Moroccan and 69 Turkish. F-tests on the r esidual sums of squares of different fits demonstrated significant effects of ethnicity on the regression of the measurement versus gestational age ( P < 0.00005). In a third order polynomial regression model the second order coefficient was significantly higher and the third order coefficient was s ignificantly lower for the Moroccan group. Conclusion: The transverse cerebellar diameter is not independent of the et hnic origin of the patient. When using the transverse cerebellar diameter f or the evaluation of fetal growth or for dating a pregnancy, care should be taken to rely on charts appropriate for the ethnic group, as demonstrated here for Moroccan fetuses.