With the ascendancy of biophysical assessment with Doppler velocimetry, and the establishment of routine scan dating in early pregnancy, there needs to be a radical re-think of the role of ultrasound biometry in the definition and assessment of fetal growth restriction (FGR).

Doppler flow velocimetry of the umbilical artery has proven its value in defining the FGR fetus. It is more useful than cardiotocography (CTG) or biophysical profile scoring. However, the sensitivity of any test depends on the prevalence of the condition being looked for. While Doppler is of value in fetuses which are small-for-gestational age (SGA), it is less useful in predicting growth restriction or adverse outcome in the general population. The question is therefore, how to detect those pregnancies for which further fetal assessment is indicated.