Introduction

There are several terms that are frequently used interchangeably for intrauterine growth retardation (IUGR). These include fetal growth retardation, fetal mal- or undernutrition, small-for-gestational-age (SGA), small-or light-for-dates, dysmature, placental insufficiency syndrome, “runting” syndrome and hypotrophy. More recently, there has been a move towards using “restriction” instead of “retardation,” because parents tend to link “retardation” with mental retardation. Unfortunately, these terms do not all mean the same thing, which has led to some confusion, both with regard to etiologic classification and also with regard to follow-up and outcome. In interpreting studies dealing with IUGR, it is important to know how the term has been defined for the particular study.

Even for studies dealing with infants who are called SGA, it is important to know the normative data used for comparison. For many years, the growth curves developed in Denver, Colorado, were used as the basis for comparison by many authors. It should be appreciated that these data were gathered from infants born at an altitude of 5000 ft (1525 m) and altitude may have an effect upon birth weight for gestational age. Thus, infants classified as below the 10th percentile by birth weight for gestational age in Colorado probably represent infants below the third percentile at sea level, for example using Montreal curves. More recent data from Sweden, also at sea level, indicate that birth weights in recent years may be even higher than noted in an earlier era.