Problem/Objective: Smoking during pregnancy is the leading cause of preventable adverse pregnancy outcomes. Birth certificate (BC) data provide a national estimate of smoking during pregnancy; however, smoking during pregnancy has been found to be underreported on birth certificates. The goal of this study is to provide a more comprehensive population-based estimate of the prevalence of smoking during pregnancy by combining information from two data sources: BC and a self-administered questionnaire.

Methods: We analyzed 2004 data (n=40,659) from 24 states that participate in the Pregnancy Risk Assessment Monitoring System (PRAMS), an ongoing, state- and population-based surveillance system. We compared prevalence of smoking during pregnancy using BC-alone, PRAMS-alone, and the two data sources combined. Data were weighted to represent all women delivering live births in each state during 2004. Descriptive statistics were computed using SAS callable SUDAAN.

Results: The mean age of respondents was 27 years, 62% were married, 53% were non-Hispanic White, 56% were pregnant with their second or greater child and 81% had 12 years of education or more. The combined data sources indicated 14.6% (95%CI, 14.1%, 15.1%) of women reported smoking during pregnancy; an increase of 44.8% over the prevalence of smoking during pregnancy as indicated on BC-alone (10.1%; 95%CI: 12.3%, 13.4%) and 13.6% over PRAMS-alone prevalence (12.8%; 95%CI: 12.3%, 13.4%).

Conclusions: Based on BC and PRAMS data from 24 states, the number of infants exposed to tobacco in-utero may be 44.8% higher than is currently reported on BC.