The Impact of Measurement of Mid Thigh Soft Tissue Thickness on the Accuracy of Estimated Fetal Weight on Term Pregnancy

Abstract

Summary A ccurate EFW at delivery is crucial to evaluate the risk of morbidity and mortality in the fetus and neonate. In everyday obstetrical practice, EFW is a key tool for identifying and managing both small fetuses (BW ≤ 2500 g) and large fetuses (BW ≥ 4000 g). More specifically, fetal weight estimation may prove of paramount importance to the diagnosis and management of macrosomia, which is associated with birth trauma, asphyxia and maternal morbidity. Also, when dealing with anticipated preterm delivery, perinatal counselling on likelihood of survival, the intervention undertaken to postpone preterm delivery, optimal route of delivery, or the level of hospital where delivery should occur may be based wholly or in part on the estimation of expected birth-weight. Categorization of fetal weight into either small or large for gestational age may lead to timed obstetric interventions that collectively represent significant departure from routine antenatal care. Despite the use of more than 50 different formulae to estimate fetal weight, their performance has been poor at the extremes of fetal weight. Over the past 20 years there has been emerging interest in studying fetal soft tissue measurements to improve detection of growth abnormalities. Since fat content correlated directly with energy stores, the fat mass and lean body mass are often used in the nutritional assessment of an individual. Fat constitutes 12-14% if birth weight and has been shown to account for variations noted in neonatal weight. Consequently, ultrasound-generated estimates of fetal fat tissues may be useful in the evaluation of fetal growth abnormalities. Measurement of subcutaneous fat thickness is a simple technique. It may be used in predicting nutritional status antenatally as an adjunct with other standard parameters. This prospective study conducted at the Fetal Care Unit in the Ain Shams University Maternity Hospital confirms the potential of the linear measurement of mid-thigh STT as a valuable parameter in the sonographic assessment of fetal growth and EFW. The technical aspects of this measurement have been investigated to assess its reliability and reproducibility. This measurement has proven easy to make and has great reproducibility. Over the study period, 120 women met all the inclusion criteria. All pregnant women were corporated within the study had the following means and SD's, age 28.79±3.56 (range21 – 38ys), gestational age 37.84±0.82 (range 37 - 39) and the amniotic fluid index 10.05±1.58 (range 6- 14).