A representative cohort of approximately 1,800 children born in Pelotas, Southern Brazil, in 1982, is being studied prospectively. Approximately 81% of them were located at home at ages 9 to 15 months. During these interviews mothers or guardians were asked about the child's birth weight. This figure was later compared to the actual birth weight which was available from the previous phase of the study. Just over 60% of the mothers recalled the exact weight, about 80% gave weights within 100 g of the real value and 90% were within 250 g. Reported birth weights were not biased towards increasing or decreasing the true birth weight. Answers were less accurate in low-income families but these differences were not very marked, with 76% of the poorest mothers being within 100 g of the real weight, against 82 to 86% among the richest mothers. On the other hand, mothers who never attended school were more likely to be significantly off the mark in the information provided - 63% within 100 g - than mothers with complete secondary education - 84% within 100 g. It is suggested that recall information on birth weight may be useful for children under one year in similar populations within the context of epidemiological studies, but that the use of such data for individual clinical decisions may be unwarranted.
Birth weight; Longitudinal studies; Mothers