Current knowledge on the use of ultrasound measurements of fetal soft tissues for the assessment of pregnancy development

Abstract

Ultrasonography, with its detailed imaging of the fetus, is very widely used in obstetrics. The primary aim of ultrasound scanning in pregnancy is to limit the risk of obstetric complications by early detection of abnormalities, such as intrauterine growth restriction and macrosomia. Currently, morphometric formulae are used for estimating fetal weight. They utilize basic biometric parameters. However, Hadlock formula, used for fetal weight estimation, has an error rate of 20%. For this reason, researchers all over the world have been looking for other sonographic parameters correlating with fetal weight, with a higher predictive value. The current scientific reports indicate that new sonographic parameters, such as soft tissue thickness values, are useful for fetal weight assessment. The measurements can be conducted in various parts of the fetus’s body, e.g. thigh, upper arm, abdomen or the subscapular area. Different types of measurements are characterized by different levels of correlation with other sonographic and anthropometric parameters as well as body mass and gestational age. Based on the reports, numerous studies proposing new fetal weight calculation formulae have been produced. Apart from soft tissue, some more advanced and detailed measurements are taken, such as those involving adipose and lean tissue or using three-dimensional ultrasound (3D), for determining fetal weight. Ultrasound measurement of subcutaneous tissue thickness in various parts of the body may prove to be a strong predictor of fetal weight, which is useful for sonographic assessment of pregnancy.

Better Predictor of Fetal Weight: Mid-Thigh Soft- Tissue Thickness Versus Hadlock’s Method – A Prospective Observational Study

“…However, several studies conducted show a positive correlation between the two values, and FASTT is considered to be the strongest predictor of fetal weight when measured accurately. [10] A study conducted by Forouzmehr et al showed that there was a significant difference of FASTT between the normal and macrosomic babies (6.6 mm vs. 12 mm, respectively; P < 0.001). [11] Similar results were obtained by the study conducted by Petrikovsky et al where the difference between FASTT of normal and macrosomic babies was found to be 7 mm versus 12.4 mm, P < 0.0001.…”

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“…Because subcutaneous tissue contains 75% of the body's fat. Predicting macrosomia can be done by using various ultrasonographic parameters including mid-thigh soft tissue thickness (STT), fetal abdominal subcutaneous tissue thickness (FASTT), and subscapular soft tissue thickness [2]. The major goal of this study was for comparing Hadlock's technique and MTSTT estimates of fetal weight with those of actual birth weight [18].…”

Sonographic Assessment of Fetal Growth Abnormalities

“…positive predictive value for determining a GA of greater than 37 weeks (40). Finally, fetal subcutaneous tissue measurements may prove useful for validating the GA, assessing fetal metabolic reserve, and predicting the neonatal outcome of fetuses with growth abnormalities (Fig 13) (41)(42)(43). Published nomograms show that lateral abdominal wall thickness increases linearly, approximately 0.19 mm per week, with gestation (41).…”