Fetal growth and birthweight standards as screening tools: methods for evaluating performance.

Area of Science:

• Perinatal epidemiology
• Obstetric clinical practice
• Biostatistics

Background:

• Accurate fetal growth assessment is crucial for both clinical management and epidemiological research.
• Existing standards for fetal growth and birthweight have varying utility depending on their application.
• Population-based data are essential for establishing reliable growth and birthweight benchmarks.

Purpose of the Study:

• To compare the performance of fetal growth standards and population-based birthweight standards.
• To evaluate these standards for distinct applications: antenatal care and epidemiological studies.
• To determine the optimal method for assessing fetal well-being and population health.

Main Methods:

• A population-based cohort study utilizing routinely collected data from Scotland.
• Inclusion of 540,849 singletons born after 24 weeks gestation between 1980 and 2003.
• Comparison of standards using measures of screening and diagnostic performance (sensitivity, specificity, PPV, NPV) for stillbirth risk and rates.

Main Results:

• For antenatal care, fetal growth standards demonstrate higher sensitivity (30-43%) in detecting stillbirth risks compared to birthweight standards (29%).
• Positive predictive values for stillbirth risk are low (~1%) across gestations for both standards.
• For epidemiology, population birthweight standards show higher sensitivity and specificity for preterm births, but this advantage diminishes for term births.

Conclusions:

• The choice of standard for evaluating fetal growth and birthweight is dependent on the intended use.
• Fetal growth standards are recommended for antenatal care due to better stillbirth risk detection.
• Different evaluation metrics are necessary for epidemiological investigations versus clinical applications.