Ratios between the abdominal circumference, head circumference, or femur length and the transverse cerebellar diameter of the growth-retarded and macrosomic fetus.

The purpose of our investigation was twofold: to provide normative data for the ratios between head circumference and cerebellum, abdominal circumference and cerebellum, and femur length and cerebellum; and to evaluate the predictive accuracy of an abnormal ratio in the detection of growth retardation and macrosomia. Data on 675 women with normal gestations between 14 and 42 weeks were used to estimate reference curves for the three ratios to be evaluated. We then compared the ratios of 34 fetuses with intrauterine growth retardation and 28 macrosomic fetuses to the control group. Of the three ratios that we investigated, abdominal circumference to transverse cerebellar diameter was the most efficacious. However, the sensitivity of this ratio for the detection of intrauterine growth retardation and macrosomia was only 52.9% and 46.6%, respectively. A ratio between head circumference, abdominal circumference, or femur length and the transverse cerebellar diameter cannot reliably distinguish between normally growing fetuses and those that are growth retarded or macrosomic.