Sonographic diagnosis of fetal head deflexion and the risk of cesarean delivery.

BACKGROUND

Malpositions and deflexed cephalic malpresentations are well recognized causes of dysfunctional labor, may result in fetal and maternal complications, and are diagnosed more precisely with an ultrasound examination than with a digital examination.

OBJECTIVE

This study aimed to assess the incidence of malpositions and deflexed cephalic malpresentations at the beginning of the second stage of labor and to evaluate the role of the sonographic diagnosis of deflexion in the prediction of the mode of delivery.

STUDY DESIGN

Women in labor with a singleton pregnancy at term with fetuses in a cephalic presentation at 10 cm of cervical dilatation were prospectively examined. A transabdominal ultrasound was performed to assess the fetal head position by demonstrating the fetal occiput or the eyes. Deflexion was assessed by the measurement of the occiput-spine angle when the occiput was anterior or transverse and by qualitative assessment of the relationship between chin and thorax when the occiput was posterior. Transperineal ultrasound was performed in occiput posterior fetuses to discriminate between sinciput, brow, and face presentation. Maternal, labor, and neonatal parameters including maternal age, induction of labor, use of epidural, birthweight, arterial pH, and neonatal intensive care unit admission were recorded. Patients were divided into 2 groups according to the sonographic diagnosis of head deflexion. Adjusted odds ratios were calculated using multivariate logistic regression to determine the association between cesarean delivery and the 2 groups. In addition, labor and neonatal characteristics were compared between occiput anterior and occiput posterior-occiput transverse fetuses.

RESULTS

Of the 200 women at the beginning of the second stage, the fetus was in occiput anterior position in 156 (78%), transverse in 11 (5.5%), and posterior in 33 (16.5%) cases. Deflexion was diagnosed in 33 of 156 (21.2%) occiput anterior fetuses and 19 of 44 (43.2%) occiput posterior and occiput transverse fetuses. Cesarean deliveries were significantly associated with fetal head deflexion both in occiput anterior (P=.001) and occiput posterior (P<.001) fetuses. Sonographic diagnosis of fetal head deflexion was an independent risk factor for cesarean delivery both in occiput anterior (adjusted odds ratio, 5.37; 95% confidence interval, 1.819-15.869) and occiput posterior (adjusted odds ratio, 13.9; 95% confidence interval, 1.958-98.671) cases, and it was an independent risk factor for cesarean delivery regardless of the occiput position (adjusted odds ratio, 5.83; 95% confidence interval, 2.47-13.73).

CONCLUSION

The sonographic diagnosis of fetal head deflexion at the beginning of the second stage increases the risk of cesarean delivery.