Accuracy and correlates of maternal recall of birthweight and gestational age

Objective: To determine the accuracy of maternal recall of children birthweight (BW) and gestational age (GA), using the Danish Medical Birth Register (DBR) as reference and to examine the reliability of recalled BW and its potential correlates. Design: Comparison of data from the DBR and the European Youth Heart Study (EYHS). Setting: Schools in Odense, Denmark. Population: A total of 1271 and 678 mothers of school children participated with information in the accuracy studies of BW and GA, respectively. The reliability sample of BW was composed of 359 women. Method: The agreement between the two sources was evaluated by mean differences (MD), intraclass correlation coefficient (ICC) and Bland-Altman's plots. The misclassification of the various BW and GA categories were also estimated. Main outcome measures: Differences between recalled and registered BW and GA. Results: There was high agreement between recalled and registered BW (MD = -0.2 g; ICC = 0.94) and GA (MD = 0.3 weeks; ICC = 0.76). Only 1.6% of BW would have been misclassified into low, normal or high BW and 16.5% of GA would have been misclassified into preterm, term or post-term based on maternal recall. The logistic regression revealed that the most important variables in the discordance between recalled and registered BW were ethnicity and parity. Maternal recall of BW was highly reliable (MD = -5.5 g; ICC = 0.93), and reliability remained high across subgroups. Conclusion: Maternal recall of BW and GA seems to be sufficiently accurate for clinical and epidemiological use.