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Estimating Gestational Age With Sonography: Regression-Derived Formula Versus the Fetal Biometric Average
Chase R Cawyer1, Sarah B Anderson1, Jeff M Szychowski1
1Center for Women's Reproductive Health, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Summary
A new regression formula for fetal age estimation is more accurate than the Hadlock average method, especially after 29 weeks. This improved accuracy in gestational age (GA) prediction benefits prenatal care.
Area of Science:
- Maternal-Fetal Medicine
- Diagnostic Ultrasound
- Biometry
Background:
- Accurate gestational age (GA) estimation is crucial for optimal prenatal care and management.
- Existing methods for GA calculation include regression-derived formulas and averaging biometric measurements.
- The National Fetal Growth Studies data provides a basis for developing new, potentially more accurate, fetal growth assessment tools.
Purpose of the Study:
- To compare the accuracy of a novel regression-derived formula using National Fetal Growth Studies data against the conventional Hadlock average method for estimating gestational age.
- To evaluate the performance of both methods across different gestational age intervals.
Main Methods:
- A retrospective cross-sectional study of 16,904 sonograms from nonanomalous singleton pregnancies.
- Gestational age was referenced using crown-rump length.
- Error in GA estimation was calculated for the National Institute of Child Health and Human Development (NICHD) regression formula and the Hadlock average method.
- Errors were compared in three GA intervals: 14–20 weeks 6 days, 21–28 weeks 6 days, and ≥29 weeks.
Main Results:
- The NICHD regression formula demonstrated significantly smaller mean errors overall and within prespecified GA ranges compared to the Hadlock average method (P < .01).
- The regression formula had significantly lower odds of examinations with errors outside the specified range in GA intervals 2 (OR, 1.15; 95% CI, 1.01–1.31) and 3 (OR, 1.24; 95% CI, 1.17–1.32).
Conclusions:
- The NICHD regression formula provides more accurate gestational age estimates than the Hadlock average method in a contemporary, unselected population.
- The improved accuracy of the regression formula is most notable for gestational age estimates at 29 weeks and later.
- These findings suggest the NICHD regression formula may enhance the reliability of fetal dating in clinical practice.
Keywords:
Hadlock averageNational Fetal Growth StudiesNational Institute of Child Health and Human Development Formulagestational ageobstetricsMore Related Videos
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