Population-based surveillance and prevalence of stillbirths: Iowa Stillbirth Surveillance Project (ISSP)
Introduction: In the United States, stillbirth prevalence is commonly estimated from fetal death certificates (FDCs) with reports of 6/1,000 deliveries. FDC reporting is guided by the Model State Vital Statistics Act and Regulations (Model Law), which recommends defining a fetal death as a stillbirth if delivery weight was ≥350 grams or gestation was ≥20 weeks. Each state, however, develops its own FDC criteria, which limits its use for generating national estimates.
Methods: An alternative to FDCs is use of birth defect surveillance systems to identify stillbirths. In 2005, the ISSP engaged the Iowa Registry for Congenital and Inherited Disorders to conduct population-based stillbirth surveillance among nearly 40,000 deliveries annually. Iowa defines a reportable stillbirth per the Model Law. Using this definition, we conducted multisource surveillance (e.g., FDCs, perinatal reports, inpatient and outpatient records) and estimated stillbirth prevalence (N stillbirths/N live birth+stillbirth deliveries) in Iowa.
Results: From 2005-2011, we ascertained 1,363 reportable stillbirths among 278,666 deliveries, producing an overall prevalence of 4.9/1,000 deliveries; annual estimates ranged from 4.2 to 5.9. Our multisource ascertainment verified that 82% of FDCs issued were for reportable stillbirths. Additionally, 15% of all reportable stillbirths were not issued a FDC.
Conclusions: Our population-based estimates for stillbirths tend to attenuate those previously reported. Our approach can serve as a model for other states to conduct stillbirth surveillance. To this end, we recently expanded to birth defect surveillance systems in Colorado, Hawaii, and New York State, and now annually monitor more than 120,000 deliveries with a diverse racial/ethnic composition.