Introduction

Although intrauterine growth restriction (IUGR) has only recently been consistently distinguished from low birth weight (LBW) and prematurity, this distinction has been crucial in our understanding of the causes and consequences of small size at birth and of interventions that might be successful in reducing the incidence and severity of this condition. To provide background information for subsequent chapters, concepts about the etiology of IUGR will be discussed here. The causes of IUGR in diverse circumstances will be presented, along with implications for preventing this condition in American population groups. This chapter focuses primarily on nutritional and behavioral factors, such as smoking, related to IUGR. Other factors related to IUGR are considered in Chapter 7.

Infants who are small at birth also have been described as “small-for-date” or as “small-for-gestational-age.” Most recently, they have been described as having “fetal growth restriction.” In this paper, the term IUGR will be used synonymously with these other terms, although – strictly speaking – this is not correct (Altman and Hytten, 1989).

Definition of intrauterine growth restriction

In classifying infants as having IUGR, we are trying to identify those individuals whose growth, in the simplest terms, is less than their genetic potential. This is not easy to do because it is difficult to know a particular individual's genetic potential for growth.