Can the anterior-posterior thigh diameter be used as an indicator for fetal age using two-dimensional sonography?
This study evaluates the usefulness and direct correlation of a new method of predicting fetal age by the measurement of the anteriorposterior high diameter (APTD) in normal 18 to 28 week pregnancies using two-dimensional sonography. Little published research exists in the area of fetal thigh biometry, specifically in the use of the APTD. The only study the author found was that of fetal thigh circumference. Continuing review of existing practices needs to be coupled with evaluation of alternate or additional methodology.
Material and methods:
This was a quantitative prospective study of 55 patients in a hospital in Alberta, Canada. APTDs were sonographically
measured. The normal range for each week of pregnancy was determined for reliability.
Results: Significant correlation was found between the APTD and fetal age from simple line regression analysis, with 99.9% confidence intervals at each week from 18 to 28 weeks gestation. There was a correlation of 1 mm APTD per one week of fetal age. In addition R >0.93, P< than 0.001. The residual scatter plots confirmed the APTD validity.
Conclusion: APTD is a reliable and valid method for assessing fetal age in a normal pregnancy and may be particularly useful when other parameters are unable to accurately predict fetal age. An accurate linear measurement of multiple fetal parameters allows a more complete profile of fetal growth and estimated date of delivery. APTD may also be useful in identifying fetal growth problems. All of the values of fetal age lie directly on the best-fit regression line. Since the coefficient of determination (Rsq) is very high, this model is very effective.
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