Validation of obstetric estimate of gestational age on US birth certificates

Objective The birth certificate variable obstetric estimate of gestational age (GA) has not been previously validated against GA based on estimated date of delivery from medical records. Study Design We estimated sensitivity, specificity, positive predictive value, negative predictive value and the corresponding 95% confidence intervals (CIs) for preterm delivery ( Results In New York City, the preterm delivery rate based on estimated date of delivery was 9.7% (95% CI, 7.6–12.4) and 8.2% (95% CI, 6.3–10.6) based on obstetric estimate; in Vermont, it was 6.8% (95% CI, 5.4–8.4) based on estimated date of delivery and 6.3% (95% CI, 5.1–7.8) based on obstetric estimate. In New York City, sensitivity of obstetric estimate-based preterm delivery was 82.5% (95% CI, 69.4–90.8), specificity 98.1% (95% CI, 96.4–99.1), positive predictive value 98.0% (95% CI, 95.2–99.2), and negative predictive value 98.8% (95% CI, 99.6–99.9). In Vermont, sensitivity of obstetric estimate-based preterm delivery was 93.8% (95% CI, 81.8–98.1), specificity 99.6% (95% CI, 98.5–99.9), positive predictive value 100%, and negative predictive value 100%. Conclusion Obstetric estimate-based preterm delivery had excellent specificity, positive predictive value and negative predictive value. Sensitivity was moderate in New York City and excellent in Vermont. These results suggest obstetric estimate-based preterm delivery from the birth certificate is useful for the surveillance of preterm delivery.