Determinants of catch-up growth in small-for-gestational age infants

Objective. To identify predictors of catch-up growth during the first year of life among small for gestational age (SGA) infants in a developing country setting.Design. Cohort study, with follow-up visits at 1, 3, 6 and 12 months.Setting. Pelotas, a southern Brazilian city.Population. SGA infants who were born in 1993 and whose families lived in the urban area of Pelotas.Main outcomes. Weight and length gain from birth to 6 months and from 6 to 12 months.Results. Two hundred twenty term SGA infants were targeted for follow-up, which was achieved for 205 (93.2%) infants at 12 months. At 6 months, the proportion of infants with weight-for-age and length-for-age z-scores <-1.28 SDS was 18.9% and 37.8%, respectively. At 12 months, the proportion of children with a weight-for-age z-score <-1.28 SDS increased to 35.2%, whereas for length-for-age this proportion remained about the same as it had been at 6 months. Severity of intrauterine growth retardation, body proportionality at birth, maternal remunerated work after delivery, maternal age, parity, maternal prepregnancy body mass index and maternal smoking during pregnancy had no significant effect on postnatal growth in the first year of life. Those infants who were weaned by 1 month had faster weight and length gain by 6 months. Socioeconomic status (SES) modified the effect of breast feeding duration on weight and length gain in the first 6 months of life. Among high-SES families, those children who were weaned by 1 month gained 578 g more than those still breast feeding at 6 months. Among low-SES families, however, those children who were weaned by 1 month gained 349 g less than those still breast feeding at 6 months. Those children who were weaned by 6 months had faster weight gain from 6 to 12 months, and this association was not modified by SES, while low SES was associated with slower weight and length gain in the same period. Children of short (<150 cm) mothers gained 1.31 cm less (95% confidence interval -2.52 to -0.1) by 6 months than those of mothers >160 cm. Children who were hospitalized showed a nonsignificantly slower length gain throughout the first year of life.Conclusion. SGA infants experienced catch-up growth for weight and length but remained shorter and lighter than those in the NCHS reference population at both 6 and 12 months of age. Socioeconomic status and infant feeding were the main determinants of catch-up growth