Is The Clock Position Method Practical And Accurate To Determine The Axis Of The Fetal Heart? Comparison With The Bronshtein (Right-Hand Rule) Method

ABSTRACT
Objective: This study aimed to compare the evaluation time and accuracy of the Clock position method and the Bronshtein method for determining the fetal heart axis among first-year obstetrics and gynecology residents.
Materials and Methods: This prospective study was conducted at Ankara Etlik City Hospital between February 2024 and June 2024. Thirty-seven first-year obstetrics and gynecology residents evaluated four fetuses with the following presentations: vertex, breech, transverse, and vertex with situs inversus. Each participant determined the fetal heart axis using both the Clock position method and the Bronshtein method. In the Clock position method, the fetal thorax is visualized as a clock, with the fetal spine always positioned at 12 o’clock. In vertex presentation, the fetal heart is located at the 5 o’clock position, whereas in breech presentation, it is at the 7 o’clock position. The evaluation time and the accuracy of fetal heart axis assessment were recorded.
Results: The Clock position method was significantly faster than the Bronshtein method across all fetal positions (p < 0.001 for all comparisons). The shortest evaluation time using the Clock method was in the vertex position (17 seconds, 11–22), while the longest was in situs inversus cases (22 seconds, 15–27). In contrast, the Bronshtein method required significantly longer evaluation times, with the shortest duration in the vertex position (28 seconds, 23–38) and the longest in the transverse position (76 seconds, 40–90). The Clock method demonstrated 100% accuracy across all positions, whereas the Bronshtein method showed lower accuracy, particularly in situs inversus cases (81.1%).
Conclusion: The Clock position method is a faster and more accurate approach for fetal heart axis determination than the Bronshtein method. Its simplicity, independence from fetal movements, and reduced cognitive load make it a valuable technique for obstetrics and gynecology residents, particularly those in the early stages of training. 
Keywords: Clock position method, bronshtein (right-hand rule) method, fetal heart, heart axis