Antepartum detection of macrosomic fetus: clinical versus sonographic, including humeral soft tissue thickness

Abstract EN

Objective : to compare clinical and sonographic estimation of birth weight using Hadlock's (1) equation with new estimation technique that involve measurement of fetal humeral soft tissue thickness to identify newborns with birth weight of at least 4000g.

Patients and Methods : A prospective study conducted in Gynaecology & Obstetrics Department in Al-Yarmook Teaching Hospital, Baghdad, Iraq.

Ninety pregnant women were studied between October 2003 and September 2004.

They had gestational ages of 37 weeks or more and a suspicion of fetal macrosomia based on the presence of one or more of certain risk factors.

Clinical estimation of fetal body weight using Leopold's manoeuvre was done followed by sonographic fetal weight estimation using Hadlock's (1) equation.

Fetal humeral soft tissue thickness (the distance from the outer edge of the humerus to the skin surface on transverse views of the upper arm) was measured by ultrasound.

Then a comparison of the three methods mentioned above was done regarding their validity in predicting fetal macrosomia. Results : sonographic fetal humeral soft tissue thickness correlates with birth weight and found to be higher in macrosomic than the non-macrosomic newborns (14.35mm versus 11.6mm) and the difference was statistically significant (P value <0.00). The sonographic fetal humeral soft tissue thickness measurement was more sensitive in predicting fetal macrosomia than the sonographic fetal weight estimation (87.2 versus 75%) but less specific (74.2 versus 86%).

The positive predictive value was 84.2 versus 89% and the negative predictive value was 78.7 versus 68% respectively while the clinical estimation had the lowest accuracy in predicting fetal macrosomia compared with sonographic fetal weight estimation and sonographic fetal humeral soft tissue measurement. Conclusion : the sonographic measurement of fetal humeral soft tissue thickness positively correlates with newborn birth weight.

It is more accurate than the clinical fetal weight estimation in predicting fetal macrosomia.

On the other hand it is more sensitive but less specific than the sonographic fetal weight estimation using Hadlock's (1) equation in predicting fetal macrosomia.