APTD

The Regression Line for APTD

The residual (Error), Scatter plot and Validity of the (APTD)

Sagittal plane of the fetal thigh show the femur length with one of the calipers in the mid point of the femur length

The first caliper is moved to the real outer skin of the anterior wall of the fetal thigh

The sagittal section of the fetal thigh is showing the measurement of the femur length. The arrow is showing the fetal knee. Magnification can be a helpful tool

The second caliper is moved to the posterior wall of the fetal thigh. Enter and log the measurement of the anterior posterior thigh diameter (APTD)

Label A is showing the wrong way to measure fetal thigh (coronal) and Label B is showing the correct way to measure the anteriorposterior thigh diameter (APTD) in the sagittal plane (profile).

The white arrow is showing the double line of the fetal thigh. The correct measurement of the anterior-posterior thigh diameter would be the second line marked by the number (1) arrow in the real anterior wall of the fetal thigh, as this is the true skin line. The second line marked by number (2) arrow is part of the thigh tissue as the sound waves travels through the convex area, and can be corrected by scanning in a good sagittal plane.

Measurements of femur lengths from the 55 patients who met the criteria were correlated with the anterior-posterior thigh diameter (APTD) and used to construct tables and graphs. There was significant correlation between the anterior-posterior thigh diameter (APTD) and fetal age. Using a simple linear regression for this study, more than 99.993 % confidence intervals were found at each week of the eleven groups from 18 to 28 weeks gestation (Rsq > 0.9993), and (p less than 0.0001). The anterior-posterior thigh diameter was positively correlated with fetal age [] and [, , & ]. Eleven gestational periods from 18 to 28 weeks were analyzed, each period including 5 different measurements of the femur lengths compared to the fetal age and to the anterior-posterior thigh diameter with mean +/−2SD. Femur length measured from 2.70 centimetre (cm) to 5.50 cm over all gestational periods, the mean being 4.31–4.35. Fetal weight ranged between 310 grams and 1400 grams, the mean being 629 grams. The anterior-posterior thigh diameter (APTD) ranged between 1.80 to 2.87 cm, with the mean at 2.36 cm. Linear growth was obtained in each gestational period from 18 to 28 weeks, and compared favourably with the Dr. Hadlock’s tables., In addition, linear growth of fetal weight was observed. The anterior-posterior thigh diameter, converted to millimetres and compared with the fetal age, was found to be a consistent and valid measurement by using the scatter plots [ & ]. The standard errors of estimates using anterior-posterior thigh diameter (APTD) were significantly lower (at 0.08664) than that using femur length at 0.2436. The variability estimates from Dr. Hadlock et al.’s table for femur length versus fetal age from 18 to 30 weeks have indicated ± 1.8 weeks to 2.4 weeks. The APTD table in this study shows ± 3 days variability. The adjusted R square (variance) was >.99 for both models.