9 - Diagnosis of Intrauterine Growth Retardation Using Ultrasound

Abstract

Ultrasound has been developed in the last twenty years to become the major instrument for diagnosis of intrauterine growth retardation. However, currently available commercial instruments cannot be used to their full advantage without accurate early ultrasonic measurement of gestational length and without at the same time screening for multiple pregnancy and fetal malformation. Once this has been done, methods that take account of changes in body proportion become less important in the diagnosis of IUGR in later pregnancy and formulas that allow accurate weight categorization can be used with advantage. If an ultrasonic method for screening a whole population is required, then weight-categorization formulas are now well researched and provide an acceptable margin of low false positive rates. The formula should, however, be adapted to give a measure of weight deviation rather than absolute weight so that it can be used over a period of time in pregnancy and not only in a specific week. If a non-ultrasound method is to be used for selecting a population at higher risk, conventional risk criteria (Hobel et al, 1973) and symphysisfundus measurements are valuable. Ultrasound fetometry may then be used with very high sensitivity to improve the identification of those fetuses at risk, but critical evaluation of the use of ultrasound in this situation is still needed. The basic measurement techniques of BPD and fetal trunk measurements singly or combined into weight prediction formulas could then, in larger reference laboratories, be supplemented by ancillary ultrasonic means of investigating fetal growth and fetal well-being. An adverse fetal environment preceding measurable growth retardation of the fetus itself can possibly be reflected in a decrease of intrauterine volume and amniotic fluid and changes of fetal well-being could be investigated by means of changes in volume parameters, fetal activity or fetal blood flow. The next steps towards improved ultrasonic evaluation of IUGR fetuses are likely to be in this direction, while increased IUGR detection will mainly result from better screening techniques.