Validity of Maternal Report of Birthweight in a Cohort Study and Its Implication on Low Birthweight Rate Using Simulations

OBJECTIVE: Maternal recall of birthweight is a convenient and cost-effective way to obtain birthweight measurements when official records are unavailable. It is important to assess the validity of maternal recall of birthweight before using these measurements to draw conclusions about a population. METHODS: This is secondary analysis of data from a previous cohort study. We analyzed actual and reported birthweights of 200 mother-and-child pairs from Southern India. We validated maternal report of birthweight by generating correlation coefficients, summary statistics, and Bland-Altman plots. We ran simulations to evaluate how misclassification as low or normal birthweight changed with the mean birthweight of the cohort. RESULTS: Reported birthweight was strongly correlated with actual birthweight (r=0.80, P<0.001); 55%, 78.5%, and 93% of subjects reported values within 50 g, 250 g, and 500 g, respectively of actual birthweight. None of sociodemographic covariates was significantly associated with the accuracy of maternal recall of birthweight. 7.5% of children were misclassified as either low or normal birthweight by reported birthweight. Simulations revealed that increasing the reported and actual birthweights by 500g reduces the misclassification rate from 7.5% to 1.5%. CONCLUSIONS: Maternal recall is a sufficiently accurate measure of actual birthweight. However, the distribution of actual birthweight in the population must be taken into consideration when classifying babies as low or normal birthweight, especially in populations where mean birthweight is close to 2500g.