Anterior-Posterior Thigh Diameter Measured by Two-Dimensional Sonography : Indicator of Fetal Age at 18 to 28 Weeks Gestation ?

Saad R I Al-Kubaisi


Objective: Little published research exists in the area of fetal thigh biometry, specifically in the use of the anteriorposterior fetal thigh diameter (APTD). A continuing review of existing practices needs to be coupled with evaluation of alternate or additional methodology. This study evaluated the usefulness and direct correlation of a simple, new method of predicting fetal age by measurement of the anterior-posterior thigh diameter (APTD) in a normal 18-to 28 week pregnancies using two-dimensional sonography. Methods: This was a quantitative prospective study of 55 patients in the High Level General Hospital, Alberta, Canada. Anterior-posterior thigh diameters (APTD) were sonographically measured and the normal range for each week of pregnancy was determined five times for reliability. Results: Significant correlation was found between (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 1 week of fetal age. The standard error of estimation was very low at (0.08664) in edition (r>0.9993) and (p < than 0.0001). 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 accurately to predict fetal age. An accurate linear measurement of multiple fetal parameters allows a more complete profile of fetal growth and estimated date of delivery (EDD). 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 thecoefficient of determination (Rsq) is very high, this model is very effective. 


Fetal age, APTD, anterior-posterior thigh diameter, parameters

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Sultan Qaboos University Medical Journal, College of Medicine and Health Sciences, Sultan Qaboos University, PO Box 35, Postal Code 123, Al-Khod, Muscat, Oman

ISSN (Print edition): 2075-051X ISSN (Internet edition): 2075-0528

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