The ‘occiput-spine angle’: a new sonographic index of fetal head deflexion during first stage of labor as predictor of course of labor and outcome

Abstract

Abstract Background Labor is a physiologic process during which the products of conception (i.e. the fetus, membranes, umbilical cord, and placenta) are expelled outside of the uterus. Labor is achieved with changes in the biochemical connective tissue and with gradual effacement and dilatation of the uterine cervix as a result of rhythmic uterine contractions of sufficient frequency, intensity, and duration. Labor is divided into three stages that include cervical dilatation, fetal delivery and delivery of the placenta. Objective The aims of this study were to quantify the degree of fetal head deflection via the use of Ultrasound during the first stage of labor and to determine whether a parameter derived from ultrasound examination (the occiput-spine angle) has a relationship with the progress of labor, subsequent effect on maternal, fetal complications and rate of cesarean delivery. Methods This is a prospective cohort study which includes a total of 200 women with gestational age 37-42 weeks were assessed in this study in Ain shams Maternity hospital labor ward by 2 dimensional ultra sound. Examinations were performed after a verbal and written consent from the patient with the patient lying in the dorsal supine position. And exclusion of Occiput-posterior position, multigravida, Indication for cesarean, Medical disorder eg hypertension or diabetes, pre labor rupture of membranes to correlate between the Occiput- spine angle (OSA) and the outcome of labor regarding the progress of labor, incidence of cesarean section, maternal and fetal complications. Results This study demonstrates that the sonographic measurement of the angle formed by the fetal occiput and the spine (occiput-spine angle) is feasible and reproducible, the occiput-spine angle in the first stage of labor is positively correlated with the clinically established station and the risk of obstructed labor requiring an operative delivery ie, Occiput-spine angle have been statistically significantly lower in cases underwent operative delivery. Occiput-spine angle had a statistically significant low diagnostic performance in predicting operative delivery. Conclusion The occiput-spine angle in the first stage of labor correlates significantly with the risk of obstructed labor Compared with spontaneous vaginal deliveries, cases that require obstetric intervention demonstrated a smaller occiput-spine angle at a similar station, suggesting diminished flexion of the fetal head. For occiput anterior fetuses, the greater the degree of fetal head deflexion, the greater risk of operative delivery due to labor arrest.