Accuracy of birth certificate data by risk factors and outcomes: analysis of data from New Jersey

OBJECTIVE: The purpose of this study was to determine the extent to which the accuracy of birth certificate data varies by risk factors and birth outcomes. STUDY DESIGN: We reanalyzed data from a validation study of birth certificate data in New Jersey, focusing on subgroups of mothers according to marital status, age, race, ethnicity, English- language proficiency, prenatal care, transfer status, birthweight, and gestational age. RESULTS: Underreporting of birth certificate data elements varies by maternal characteristics ( particularly English- language proficiency), transfer status, and birth outcomes. CONCLUSION: It is important to consider subgroup variations in data quality when birth certificate data are used for research. Additional studies are needed to explore the sources of variation in data quality and to assess the quality for additional subgroups, across subgroups in other states, in low-risk populations, and of new data items that were introduced in the 2003 revision of the US Standard Certificate of Live Birth.