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Revisiting the Hadlock 1991 population reference for estimated fetal weight
Aaron W Roberts1, Vahed Maroufy2, Ashley Salazar1
1Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston, Houston, TX.
American Journal of Obstetrics and Gynecology
|March 29, 2025
Summary
The Hadlock 1991 fetal growth standard has discrepancies between its equation and table. Using the table underdiagnoses fetal growth restriction, impacting clinical decisions for at-risk fetuses.
Area of Science:
- Obstetrics and Gynecology
- Fetal Medicine
- Medical Statistics
Background:
- The Hadlock 1991 standard is widely used for fetal growth assessment in the US.
- Discrepancies exist between the Hadlock 1991 methodology and its published critical values.
- These inconsistencies may affect clinical practice and research outcomes.
Purpose of the Study:
- To investigate discrepancies in the Hadlock 1991 fetal growth standard.
- To evaluate the impact of these discrepancies on fetal growth restriction diagnosis.
- To assess the influence on clinical practice and scientific literature.
Main Methods:
- Recalculated the Hadlock 1991 fetal weight standard from its published formula.
- Compared results from the formula to the published table values.
- Applied both methods to a large cohort of singleton ultrasounds (n=176,060).
- Reviewed literature referencing Hadlock 1991 for methodological consistency.
Main Results:
- The Hadlock 1991 equation and table yield different critical point values.
- The Hadlock table resulted in underdiagnosis of fetal growth restriction in 5.1% of cases compared to the equation.
- Literature reviews suggest studies favoring the equation were more positive towards Hadlock 1991.
Conclusions:
- The Hadlock 1991 equation and table are inconsistent.
- The table's underdiagnosis of fetal growth restriction can impact clinical interventions.
- Discrepancies may explain inconsistencies in prior research on fetal growth restriction detection.
- Preferring the Hadlock 1991 equation over table interpolation may improve detection rates.
- Further validation is needed to confirm clinical significance.
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