Ultrasound in labor and delivery.

Ultrasound may play an important role in the management of labor and delivery. Induction of labor is a common obstetric intervention, performed in about 20% of pregnancies. Pre-induction cervical length, measured by transvaginal sonography, has been shown to have a significant association with the induction-to-delivery interval and the risk for cesarean section. In the management of labor there is extensive evidence that digital pelvic examination does not provide accurate assessment of the position and descend of the fetal head both during the first but also in the second stage of labor. Several recent studies using both two- and three-dimensional ultrasound have now described objective measures of progression of the fetal head during labor. In instrumental deliveries an important determinant of a successful and safe use of vacuum and forceps is the correct determination of the fetal head position and appropriate application of the instrument. However, ultrasound studies have shown that digital examination before instrumental delivery fails to identify the correct fetal position in a high proportion of cases. The use of ultrasound is of crucial importance in performing a safe operative delivery and can help in the prediction of whether a vaginal delivery would be successful.