Comparison of pre-pregnancy weight and height recorded on birth certificates and in the Pregnancy Risk Assessment Monitoring System

Background: Pre-pregnancy obesity, body mass index (BMI, calculated from weight and height) >= 30 kg/m2, is associated with increased risk of pregnancy-related morbidity and adverse birth outcomes. By 2006, pre-pregnancy height and weight were collected on the birth certificate (BC) in 19 states representing 49% of US births, but few studies have examined the validity of these measures. The purpose of this study was to investigate the relationship between two statewide sources of pre-pregnancy height, weight, and BMI data.

Methods: Data from the Centers for Disease Control and Prevention Pregnancy Risk Assessment Monitoring System (PRAMS) were analyzed to compare self-reported pre-pregnancy height and weight and calculated BMI with the respective measures recorded on the BC among women who delivered a live birth in 2004 in Washington. ANOVA and t-tests were used to compare measures by individual sociodemographic characteristics. Pearson's correlation coefficients were calculated for correlational analyses.

Results: The study population included 1,469 PRAMS respondents. Among sociodemographic subgroups, pre-pregnancy height and weight varied most by race/ethnicity. Pre-pregnancy weight reported in PRAMS was consistently lower than on the BC. The correlation between the two measures of pre-pregnancy weight and height were strong overall (r = 0.92, 0.88, respectively) and among subgroups, as was the correlation between the BMI measures (overall r = 0.88).

Conclusions: Preliminary analysis suggests that BC measures of pre-pregnancy height, weight, and BMI are consistent with PRAMS measures and may be considered for use on a population basis in state analyses. Future work will incorporate data from other states.