Aim: To determine the quality of prenatal sonographic weight estimation, comparing breech and vertex presentations.
Method: In 147 breech presentations (BP) and 149 vertex presentations (VP), the biparietal head diameter (BPD), the fronto-occipital head diameter (FOD) and the transverse abdominal diameter (ATD) were measured. From these data, the weight was estimated, using Shepard's formula before 28 weeks and Hansmann's thereafter, and compared to the delivery weight. Both formula were modified to incorporate the virtual BPD (vBPD), derived from the BPD, FOD and the calculated head circumference. In the BP group, the role of examiner skills was evaluated, comparing the accuracy of experienced (DEGUM II qualifications) and average individuals.
Results: The accuracy for BP was nearly identical to that for VP (= 0.915 vs. = 0.929). The examiners' qualifications had a detectable but not significant influence on the results (= 0.942 vs. = 0.892).
Conclusion: Ultrasound measurements yield comparable results in both BP and VP, if the vBPD is used. In our opinion, ultrasonic weight estimation is a useful adjunct when determining the manner of delivery in BP.