الفهرس 
Role of Obstetric Ultrasound in Detection of Gestational Age and Fetal WeightOnly 14 pages are availabe for public view
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Abstract
F
etal weight estimation by ultrasound is an important factor in obstetrics; it is directly related to the gestational age which helps to plan the mode of delivery and labor management.
It gives the information about intrauterine growth restriction (IUGR) and has a significant role in the prevention of prematurity. It also helps to control the rate of perinatal morbidity and mortality.
There are many methods to find out the birth weight and many studies have been done to find out which one is more accurate. There are two main methods which include, sonographic or ultrasound method and the clinical method.
A clinical method includes the height of the uterus and girth of the abdomen at the level of umbilicus but this method has a major number of errors and not useful for polyhydramnios, oligohydramnios, maternal obesity, malpresentation, and multifetal pregnancy.
In ultrasound, Head Circumference (HC), Abdominal Circumference (AC), Femur Length (FL) and Bi-parietal Diameter (BPD) are used for fetal weight estimation.
These ultrasonographic parameters (Head circumference, abdominal circumference, Femur length and Biparietal diameter) are more accurate than the clinical method. These parameters are used with different formulas, either alone or in combination and provide somewhat accurate birth weight estimation.
In addition to these sonographical biometric parameters, a new parameter has been introduced which is the fetal thigh circumference (FTC) by Hoffbauer and workers. Thigh circumference is more reliable method for accurate fetal birth weight estimation; it also detects the changes in the soft tissue masses.
Vintzileos et al., reported that addition of fetal thigh circumference to the other parameters (BPD, HC, AC & FL) gave more accurate results for fetal weight Estimation predicting the actual weight within +/- 5% in 54% of the cases, and within +/- 10% in 80.3% of the cases.
Also, it was proven that there is a significant positive correlation between the abdominal subcutaneous tissue thickness (SCT) and birth weight and may be helpful in predicting abnormalities in fetal growth. During first 6 months of gestation, very little subcutaneous fat is deposited.
Between 24-40 weeks, skin fold thickness on the abdomen 1-2 cm lateral to the umbilicus increases from an average of 1.0 to 3.4 mm. Total fetal fat increases from 4% of body weight at 28 weeks gestation to 14% at 40 weeks gestation. Near term approximately 75% of body fat is found in the subcutaneous adipose tissue.
Large for gestational age fetuses are noted to have an increase in subcutaneous tissue and Growth restricted fetuses have a decrease in subcutaneous fat. Infants with Subcutaneous tissue thickness (SCT) less than 5 mm at 38 weeks were 5 times more likely to have birth weight <10th percentile and increased neonatal morbidity compared to infants with SCT 5 mm or more. The authors have not given the rationale for using 5 mm as cut-off.
Measuring one parameter that is; SCT to obtain expected fetal weight will be easier than measuring three parameters or more. It will reduce the time consumed by physician during ultrasonography. Furthermore, it will reduce the time the pregnant female lies in supine position which is discomforting for her.
Consequently, this study was conducted and aimed to compare between fetal thigh circumference and abdominal subcutaneous tissue thickness in estimating birth weight in term pregnant women.