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Fetal head prior to delivery: precise measurement, using a mathematically extrapolated frontooccipital diameter
K Passerini1, J Kurmanavicius2, T Burkhardt2
1Department of Obstetrics and Gynecology, Spitäler Schaffhausen, Schaffhausen, Switzerland. karolina.passerini@gmail.com.
Archives of Gynecology and Obstetrics
|March 5, 2022
Summary
A new method significantly improved fetal head circumference (fHC) estimation accuracy compared to newborns. Extrapolating frontooccipital diameter (FOD) enhances precision when real-time measurements are challenging.
Area of Science:
- Medical Imaging
- Obstetrics and Gynecology
- Fetal Medicine
Background:
- Accurate fetal head circumference (fHC) estimation is crucial for assessing fetal growth and well-being.
- Traditional methods can be limited by measurement variability and technical challenges during ultrasound.
- Improving fHC accuracy aids in timely clinical decision-making.
Purpose of the Study:
- To identify a method that enhances the accuracy of fetal head circumference (fHC) evaluation in term fetuses.
- To compare the accuracy of two distinct fHC estimation techniques.
Main Methods:
- Retrospective cohort study at University Hospital of Zürich (USZ) using data from 2015-2017.
- Compared two fHC estimation methods: (1) direct sonographic estimation using frontooccipital diameter (FOD) and biparietal diameter (BPD), and (2) extrapolation of FOD based on a fixed FOD/BPD ratio.
- Data included 400 ultrasound measurements (200 expert, 200 resident) compared to newborn head circumference (nHC).
Main Results:
- Method 1 resulted in underestimation of fHC (PE -3.68% to -3.78%).
- Method 2 demonstrated significantly improved accuracy with reduced underestimation (PE -1.17% to -0.95%).
- Bland-Altman analysis showed limits of agreement between -2.41 cm and 0.55 cm for fHC.
Conclusions:
- Extrapolation of the frontooccipital diameter (FOD) using a standardized ratio significantly improves fetal head circumference (fHC) measurement accuracy.
- This enhanced method offers a more reliable approach for fHC evaluation, especially when direct measurement is difficult.
- The findings suggest a practical improvement for routine obstetric ultrasound practice.
