Prematurity and Low Birthweight
Prematurity and low birthweight (LBW) constitute frequently occurring perinatal complications with potentially risky implications. Although the terms prematurity and LBW have been around for some time, the precise meaning of these terms is often confused, giving rise to misunderstanding and inaccuracies. Historically, the terms prematurity and LBW were used interchangeably (Caputo and Mandell, 1970). These investigators were referring to a gestational age of ≤ 38 weeks or less and a birthweight of ≤ 2500 g. More recently, the term very low birthweight (VLBW) has been used to designate a birthweight of ≤ 1500 g. Using the terms prematurity and LBW synonymously leads to some confusion, since every premature infant is not LBW and every LBW infant is not premature. Owing to these discrepancies a more accurate terminology has been introduced and takes into account the relationship between gestational age and weight at birth. The new designations include small for gestational age (SGA), average for gestational age (AGA), and large for gestational age (LGA). These terms distinguish an infant within the statistically normal range for gestational age or outside the normal range. Although there are additional descriptions related to gestational age—birthweight interactions (Lubchenco, 1976), SGA, AGA, and LGA are most frequently used. The cutoff point for the SGA infant is a birthweight below the 10th percentile for its gestational age. Conversely, the cutoff point for the LGA infant is a birthweight above the 90th percentile for its gestational age. All other infants are regarded as average for gestational age, regardless of their age status. In this way, clinicians and researchers can determine whether an infants’ growth is within the expected range for its age (Fig. 1).
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