Published online by Cambridge University Press: 05 February 2013
Intrauterine growth restriction (IUGR) is defined as failure of the fetus to achieve its biologically determined growth potential and is therefore likely due to an underlying pathological process . The majority of cases of IUGR are discovered during the latter part of the third trimester and are caused by a degree of placental insufficiency and therefore generally have a good perinatal prognosis. However, a minority of cases of IUGR are diagnosed earlier as a result of severe placental insufficiency, or are due to some other cause and therefore require careful consideration of the likely diagnosis before a management plan can be developed.
To illustrate the potential difficulty in managing IUGR, a comprehensive differential diagnosis of maternal, fetal, placental, and genetic factors that may cause IUGR is summarized in Tables 18.2.1–18.2.4. The list expands with new knowledge, for example the recent demonstration of epigenetic dysregulation of specific genes in the placenta that may indirectly regulate fetal growth, such as WNT2 . Identifying the underlying etiology of IUGR during the antepartum period is important both to reduce the rate of preventable perinatal losses, especially stillbirth of normally formed fetuses , and to avoid inappropriate delivery by Cesarean section for poor prognosis scenarios. Considerable advances in this area of perinatal medicine mean that increasing numbers of IUGR pregnancies are referred to maternal-fetal medicine centers for further assessment, such that increasingly accurate diagnoses are being made during the antenatal period; as such greater numbers of intact infants born with IUGR survive with careful intensive fetal monitoring, coordinated delivery, and optimal neonatal care .