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A comparison of symphysis-fundal height and ultrasound as screening tests for light-for-gestational age infants
Insights
Serial symphysis-fundal height (SFH) measurements and single fetal abdominal circumference (AC) ultrasound scans effectively predict light-for-gestational age (LGA) infants. Combining both methods enhances sensitivity for LGA prediction, though specificity decreases.
Area of Science:
- Perinatology
- Maternal-Fetal Medicine
- Diagnostic Imaging
Background:
- Accurate prediction of light-for-gestational age (LGA) infants is crucial for optimizing perinatal outcomes.
- Symphysis-fundal height (SFH) measurement is a common clinical method for fetal growth assessment.
- Ultrasound measurement of fetal abdominal circumference (AC) offers a detailed assessment of fetal size.
Purpose of the Study:
- To compare the clinical efficiency of serial SFH measurements versus a single third-trimester ultrasound AC measurement for predicting LGA infants.
- To determine the optimal use of SFH and AC measurements, individually and in combination, for LGA screening.
Main Methods:
- A comparative study evaluating serial SFH measurements against a single ultrasound AC measurement in the third trimester.
- Adjusted the lower cut-off point for AC to match the specificity of SFH for direct comparison.
- Assessed sensitivity, specificity, and positive predictive values for both methods and their combination.
Main Results:
- Ultrasound AC measurement showed slightly higher sensitivity (83%) than SFH (76%), a difference not statistically significant.
- Both methods exhibited a high false positive rate (approximately 60%), similar to clinical assessment.
- Combining both tests improved sensitivity to 93% but reduced specificity to 67% and positive predictive value to 32%.
Conclusions:
- Serial SFH measurements and single AC ultrasound are comparable in predicting LGA infants.
- Using both SFH and AC measurements together significantly increases sensitivity for LGA detection.
- Recommended using both methods if ultrasound is available; otherwise, SFH screening with ultrasound backup is a viable alternative for LGA prediction.
Abstract:
The clinical efficiency of serial measurement of symphysis-fundal height (SFH) for the prediction of light-for-gestational age (LGA) infants was compared with that of a single measurement of fetal abdominal circumference (AC) by ultrasound in the third trimester. To make the tests comparable the lower cut-off point of AC was altered until the specificity matched that of SFH. The sensitivity of the AC measurement (83%) was slightly better than that of the SFH measurement (76%) but this difference was not statistically significant. Each test had a false positive rate of about 60% which is comparable with clinical assessment. Screening with both tests and predicting LGA with abnormal results from either test improved the sensitivity to 93% but, as expected, decreased the specificity to 67% and the positive predictive value to 32%. If ultrasound facilities permit both tests should be used otherwise SFH measurements only could screen for LGA with ultrasound back-up for those with low SFH results.