Fetal head "attitude" (relationship of fetal head to spine) in the first stage of labor may have a substantial impact on labor outcome. The diagnosis of fetal head deflexion traditionally is based on digital examination in labor. Objectives: To quantify the degree of fetal head deflection via the use of Ultrasound during the first stage of labor, and the relationship with the course and outcome of labor. Patients and methods: This was a prospective study conducted at Sayed Galal Hospital,

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... ar University from June 2019 to December 2019. Nonconsecutive series of women with uncomplicated singleton pregnancies at term gestation (37 weeks or more) were submitted to trans-abdominal ultrasound during the first stage of labor. Fetal position was occipito-anterior, and the angle between the fetal occiput and the cervical spine (the occiput-spine angle) was sonographically obtained on the sagittal plane. The measurements of the occipito-spine-angle were performed offline by an operator who was blinded to the labor outcome. The intra-and inter observer reproducibility and the correlation between the occipito-spine angle and the mode of delivery were evaluated. Results: A total of 400 pregnant women were recruited, 350 of which underwent a spontaneous vaginal delivery, and 50 were submitted to cesarean delivery. The mean value of the occipito-spine angle measured in the active phase of the first stage was 126° ± 2.79° (SD). The occipito-spine angle was significantly narrower in women who underwent CS delivery due to labor arrest. A larger occipito-spine angle (i.e. >126°) showed to be significantly associated with a shorter duration of labor. Conclusion: Fetuses with smaller occipito-spine angle (<126°) were at increased risk for operative delivery.