Small for gestational age (SGA) is defined as a birth weight and/or length >2 SDs below the gender-specific population reference mean for gestational age. However, there is confusion about various aspects of this term, as recently discussed.1,2 The term “intrauterine growth retardation” (IUGR) is often used for the same condition but preferably should be restricted to poor growth during pregnancy according to intrauterine growth diagrams used in obstetrics.3 SGA after a normal duration of gestation (37–42 weeks) is usually followed by rapid growth after birth (catch-up growth). It has been demonstrated that almost 90% of term SGA infants catch up in height in the first 2 years of postnatal life.4,5 On average, the human male has a birth length of 51 cm after term gestation and a final height, in the Netherlands, of 184 cm. Thus, in the 9 months before birth, he has reached almost 30% of his adult height potential. Fetal length velocity at midgestation is >10-fold higher than pubertal peak height velocity (Fig 1). Thus, very preterm infants are exposed to extrauterine life during a period that normally is characterized by rapid intrauterine growth. To survive, their energy expenditure shifts from growth-promoting actions to survival strategies to cope with the increased requirements of unintended postnatal life. Extrauterine growth retardation (EUGR) is often the result. Preterm infants whose mothers suffered from conditions such as preeclampsia are usually already growth-retarded at birth. Nonetheless, regardless of whether the child is born SGA, very preterm infants tend to be small at term, and a considerable proportion of them even meet criteria for SGA by that age. A study among 52 … Address correspondence to J.M. Wit, MD, PhD, Department of Pediatrics, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, Netherlands. E-mail: j.m.wit{at}lumc.nl