The small baby on gestational ultrasound

The small-for-gestational age baby contributes to cases of perinatal morbidity and mortality. Establishing small-for-gestational age status on gestational ultrasound is difficult because further management is aimed at differentiating the constitutionally normal baby from the baby who has an intrinsic problem or placental insufficiency. Even when the small fetus at risk of in utero demise from uteroplacental insufficiency is accurately identified, the optimum timing and mode of delivery are ill understood and can be difficult. The risk of premature delivery has to be weighed against the risk of fetal demise from intrauterine hypoxia. This review outlines the fetal biometric indices by which the diagnosis of a fetus that is ‘small-for-gestational-age’ is made. The place of serial scans for fetal biometry and the range of functional studies for fetal surveillance are discussed. Factors that should influence the timing of delivery are mentioned, and some recent advances in fetal surveillance are highlighted.