Pathological assessment of intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a major cause of foetal and neonatal morbidity and mortality. During post mortem, the pathologist is well placed to diagnose the presence and cause of IUGR in a stillborn baby. This article describes the approach of the pathologist in diagnosing IUGR and some of the pitfalls. We distinguish between reduced growth potential (formerly symmetrical IUGR) and nutritional IUGR (formerly asymmetrical IUGR). Aetiologically, restricted growth can be of foetal, maternal and placental origin. We discuss the importance of identifying the cause of IUGR in a clinicopathological context and the pathological findings in some of the more frequent causes of IUGR presenting at post mortem. Based on an accurate gestational age, ideally determined by the obstetrician in early pregnancy, the pathologist can derive a birth weight centile. However, the pathologist is also able to identify other indicators of IUGR, such as an elevated brain/liver weight ratio, atrophic thymus and changes in other internal organs. Placental examination plays a major role in the investigation as the majority of IUGR cases have significant placental pathology. This includes pre-eclampsia-related changes, abnormalities of the villous parenchyma and pathology of the umbilical cord. The potential benefit of a meticulous workup of IUGR foetuses is to provide an explanation of the pathological condition and to identify avoidable causes.