J Karlberg, K Albertsson-Wikland, EYW Kwan, BCC Lam, LCK Low

Various studies have presented data on the timing of postnatal catch-up growth in small-for-gestational-age infants and it has been reported to take place especially during the initial three to nine months of life. The aim of this work was to characterise early post-natal growth in healthy full-term (37-42 weeks of gestation) short-for-gestational-age babies (<-2 standard deviation scores [SDS] in birth length) in more detail than has been done previously. One series represents a longitudinal growth study of 3650 full-term, healthy children born in 1973-1975, Goteborg, Sweden. Early post-natal growth was characterised in 139 children with a birth length below -2 SDS. The second series consisted of a detailed prospective six months follow-up of 41 full-term, healthy short-for-gestational-age infants born in Hong Kong from 1994-1996. For both series height was expressed in SDS using the updated Swedish growth references at birth and post-natally. In the Swedish study, 92% of the short-for-gestational-age children reached a final height above -2 SDS, and 74%, 84%, 86%, 86% and 88% were above -2 SDS in height at 2, 5, 9, 12 and 18 months of age, respectively. The mean height SDS increased from -2.5 to -1.4 during the first two months of life to reach a value of -1.0 SDS at 18 months of age. For the Hong Kong study the mean height SDS increased from -2.4 to -1.5 during the first 5 months of life, and 28%, 41%, 49%, 56%. 58%, 68%, 69%, 73%, 71% and 79% obtained a height above -2 SDS at 1, 2, 3, 4, 6, 8, 10, 12, 17 and 21 weeks of age, respectively. Identification of catchup growth behaviour could be made with some confidence at 12 weeks of age, but not earlier. For instance, an increase in length SDS of one unit or more could be noted in 12%, 24%, 33%, 33% and 33% at 4, 8, 12, 17 and 21 weeks of age, respectively. Conclusion: A vast majority (93%) of full-term, normal infants born short will reach a final height within the normal range. Most of this catch-up growth (in >80% of infants) occurs during the first six months of life in a similar pattern in both series. Growth monitoring during this early period in life seemingly gives useful information on post-natal catch-up growth behaviour in infants born short for gestational age.