Reliability of Reported Maternal Smoking: Comparing the Birth Certificate to Maternal Worksheets and Prenatal and Hospital Medical Records, New York City and Vermont, 2009

Maternalsmoking is captured on the 2003 US Standard Birth Certificatebased on self-reported tobacco use before and during pregnancy collected on post-delivery maternal worksheets. Study objectives were to compare smoking reported on the birth certificateto maternal worksheetsand prenatal and hospital medical records. The authors analyzed a sample of New York City (NYC) and Vermont women (n = 1,037) with a live birth from January to August 2009 whose responses to the Pregnancy Risk Assessment Monitoring System survey were linked with birth certificatesand abstracted medical recordsand maternal worksheets. We calculated smoking prevalence and agreement (kappa) between sources overall and by maternaland hospital characteristics. Smoking before and during pregnancy was 13.7 and 10.4 % using birth certificates, 15.2 and 10.7 % using maternal worksheets, 18.1 and 14.1 % using medical records, and 20.5 and 15.0 % using either maternal worksheetsor medical records. Birth certificateshad “almost perfect” agreement with maternal worksheetsfor smoking before and during pregnancy (κ = 0.92 and 0.89) and “substantial” agreement with medical records(κ = 0.70 and 0.74), with variation by education, insurance, and parity. Smoking information on NYC and Vermont birth certificatesclosely agreed with maternal worksheetsbut was underestimated compared with medical records, with variation by select maternalcharacteristics. Opportunities exist to improve birth certificatesmoking data, such as reducing the stigma of smoking, and improving the collection, transcription, and source of information.