Description of the sonographic pattern of head descent on the mid-sagittal plane in relation to the fetal occiput position: a quantitative approach

To describe the sonographic pattern of head descent on the mid-sagittal plane in relation to the position of the fetal occiput in unselected population of women enrolled during the second stage of labour. Single-centre prospective observational study conducted on singleton pregnancies enrolled during the second stage of labour. Patients were submitted to transabdominal and transperineal sonography, which was performed by a senior Obstetrician to evaluate the sonographic head position and station by measuring the angle of progression (AoP). The distance between the lowest edge of the symphysis and the nearest tangential point of the fetal skull was defined as tangent line (TL). A second examiner, which was blinded to the occiput position, performed posthoc HSD and TL measurements. The relationship between means of HSD and of TL and the sonographic station assessed by the AoP was evaluated and compared between OP and non-OP fetuses. Out of the 176 women included, 30 (17.05%) had sonographically ascertained OP position. Larger HSD [20.9 ± 4.3 vs. 16.7 ± 3.3 (p < 0.01)] and TL [43.4 ± 7.1 vs. 31.8 ± 7.1 (p < 0.01)] were found in OP compared to non-OP fetuses when the sonographic station assessed by means of AoP > or equal to 140 degrees. Findings from our study suggest a different pattern of head descent between OA and OP fetuses at similar head station measured by means of AoP, with OP fetuses showing larger distance from maternal symphysis. This could be of importance for the counselling for mode of delivery in OP fetuses during the second stage of labour. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.