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Sonographically estimated fetal weights: accuracy and limitation.
B R Benacerraf1, R Gelman, F D Frigoletto
1Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
American Journal of Obstetrics and Gynecology
|November 1, 1988
Summary
Ultrasonography accurately estimates fetal weight, with 74% within 10% of actual birth weight. This method shows limitations in predicting macrosomia, highlighting the need for improved diagnostic tools in obstetrics.
Area of Science:
- Perinatal medicine
- Diagnostic imaging
Background:
- Accurate estimation of fetal weight is crucial for optimal perinatal care.
- Ultrasonography is a primary tool for estimating fetal weight, but its accuracy has been debated.
Purpose of the Study:
- To evaluate the accuracy of ultrasonographically predicted birth weights compared to actual birth weights.
- To assess the performance of ultrasonography in identifying fetal macrosomia.
Main Methods:
- A study of 1301 women delivering infants within one week of an obstetric ultrasonogram.
- Comparison of ultrasonographically estimated fetal weights with actual birth weights for singleton fetuses in vertex presentation.
Main Results:
- Overall, 74% of infants had birth weights within 10% of ultrasonographic estimates, and 42% were within 5%.
- Sensitivity for detecting macrosomia (birth weight > 4000 gm) was 65% with a 90% specificity.
- Adjusting the prediction threshold to >3800 gm increased sensitivity to 82% but decreased specificity to 79%.
Conclusions:
- Ultrasonography provides a reasonable estimation of fetal weight but has inherent limitations.
- The accuracy of ultrasonography for predicting macrosomia is moderate, suggesting potential for both false positives and negatives.