Comparison of the Causes and Consequences of Prematurity and Intrauterine Growth Retardation: A Longitudinal Study in Southern Brazil

Abstract

A cohort of 5914 liveborns (99% of the city births) was followed up to the age of 4 years in Pelotas, southern Brazil. Besides the perinatal evaluation, the cohort children were examined again at mean ages of 11, 23, and 47 months. During each visit the children were weighed and measured and information on morbidity was collected. Also, multiple sources of information were used for monitoring mortality throughout the study. Of the babies with known gestational age, 9.0% were classified as intrauterine growth-retarded and 6.3% as preterm. Excluding those of unknown gestational age, 62% of low birth weight babies were intrauterine growth-retarded and 36% were preterm. Intrauterine growth retardation was statistically associated with maternal height, prepregnancy weight birth interval, and smoking, whereas preterm births were associated with maternal prepregnancy weight and maternal age. Preterm babies had a perinatal mortality rate 13 times higher than that of babies of appropriate birth weight and gestational age and 2 times higher than that of intrauterine growth-retarded babies. Infant mortality rates presented a similar pattern, with the differentials being more pronounced during the neonatal than in the postneonatal period. In the first 2 years of life intrauterine growth-retarded children were at almost twice the risk of being hospitalized for diarrhea compared with appropriate birth weight, term children, while preterm children experienced only a slightly greater risk. For pneumonia, however, both groups of children were hospitalized significantly more than appropriate birth weight, term children. In terms of growth, despite their earlier disadvantage, preterm children gradually caught up with their appropriate birth weight, term counterparts. This catch-up occurred primarily between mean ages 23 and 47 months. Intrauterine growth-retarded children, however, exhibited no such catch-up. Indeed, their average monthly growth rates between measurements were always lower than those of children in the other two groups.