Introduction: Cephalopelvic disproportion/deflexed head increases the hazard of vaginal delivery both for the mother and for the child. Protracted labour is more common in primigravid women than in multipara. Initially it was X-ray pelvimetry which was used but now a days due to advanced technology it is ultrasound which has replaced X-ray pelvimetry and it is more informative and more accurate. Aims and Objectives: (1) To quantify the degree of fetal head deflection (2) To determine whether a parameter derived from ultrasound examination has a relationship with the course and outcome of labor. Subjects and Methods: The primigravidas with 1. Low risk pregnant women at or beyond 37 weeks of gestation in the 1st stage of labour with vertex presentation with 2. Cervical Dilatation 3-6 cms and 3. The station above the ischial spine with regular contractions. Methods: From the Eligible patients, informed consent was taken. Measurement of occipitospinal angle using abdominal probe of the USG machine and readings were noted. Summary: Age of the patient, Gestational age and weight of the baby are not found to have any significant association with the outcome of the labour. patients with lower occipitospinal angle (<120°) had undergone caesarean section majority of the time (11 patients) and those with occipitospinal angle >120° had spontaneous vaginal delivery (86 patients). Conclusion: The degree of fetal head deflexion in the first stage of labour may be quantified accurately by means of transabdominal ultrasound. The occiput-spine angle width seems significantly related to the fetal head station and to the risk of obstetric intervention.

Keywords: Primigravida with Vertex Presentation; OcciputSpinal Angle and Outcome of the Labour (Lscs or Normal Vaginal Delivery).