Poor agreement between self-reported birth weight and birth weight from original records in adult women

Data from an ongoing prospective population study of women in Göteborg, Sweden, were used to assess agreement between self-reported birth weight and birth weight obtained from original delivery records of women aged 44-60 years. Of the eligible population with traced delivery records (n = 693), only 28% (n = 192) could report their own birth weight. Spearman correlation between self-reported birth weight and birth weight from original records was r = 0.76. However, a difference plot, with limits of agreement at -1,028 to 1,038 g (95% confidence limits: lower limit, -1,157 to -901 g, upper limit, 910 to 1,166 g) revealed poor agreement between methods. Of the self-reported birth weights, 53% were in error by 250 g or more, and 31% were positively or negatively discordant by 500 g or more. Application in an analysis of cardiovascular risk factors in adulthood found conflicting results between self-reported and recorded birth weights. Low reporting rate, poor reporting accuracy, and misleading findings in application led to the conclusion that self-reported birth weights from middle-aged women would not be a satisfactory replacement for birth weights from original records.