Fetal biacromial diameter as a new ultrasound measure for prediction of macrosomia in term pregnancy: a prospective observational study

Abstract

Objective: The current study aims to evaluate a simple method for sonographic measurement of the fetal biacromial diameter for prediction of fetal macrosomia in term pregnancy.

Materials and methods: The current study was a single center prospective observational study conducted in a tertiary University Hospital from January 2015 to May 2017. We included all consecutive term (37–42 weeks) pregnant women presented to the labor ward for delivery. Ultrasound parameters were measured as biparietal diameter, head circumference, transverse thoracic diameter, mid arm diameter, abdominal circumference, femur length, estimated fetal weight, and amniotic fluid index. The proposed ultrasound formula “Youssef’s formula” to measure the fetal biacromial diameter is: [Transverse thoracic diameter +2 × midarm diameter]. The accuracy of proposed formula was compared to the actual biacromial diameter of the newborn after delivery. The primary outcome of the study was accuracy of sonographic measurement of fetal biacromial diameter in prediction of fetal macrosomia in terms of sensitivity and specificity

Results: The study included 600 participants; 49 (8.2%) of them delivered a macrosomic neonates and 551 (91.8%) delivered average weight neonates. There was no statistical significant difference between the proposed fetal biacromial diameter measured by ultrasound and the actual neonatal biacromial diameter measured after birth (p = .192). The area under the curve (AUC) for prediction of macrosomia at birth based on the fetal biacromial diameter and the abdominal circumference was 0.987 and 0.989, respectively, on receiver operating characteristic (ROC) curve analysis. Using the biacromial diameter cutoff of 15.4 cm has a PPV for prediction of macrosomia (88.4%) and 96.4% sensitivity with overall accuracy of 97%. Similarly, with the abdominal circumference (AC) cutoff of 35.5 cm, the PPV for prediction of macrosomia (87.7%) and 96.4% sensitivity with overall accuracy of 96.83%. No statistical significant difference between both of them was observed for prediction of fetal macrosomia (p = .841)

Conclusions: The sonographic measurement of fetal biacromial diameter seems to be a new simple and accurate method for prediction of fetal macrosomia and shoulder dystocia at birth.

Keywords:

• Macrosomia
• shoulder dystocia
• biacromial diameter
• ultrasound

Disclosure statement

The authors declare that they have no conflict of interest.