• angle of progression;
  • forceps;
  • head direction;
  • intrapartum ultrasound;
  • labor;
  • progression distance



To evaluate the hypothesis that intrapartum ultrasound (ITU) measurements, including the angle of progression (AOP), progression distance (PD) and head direction (HD), can predict complicated forceps delivery in non-occiput posterior deliveries.


In this prospective observational study, a single operator performed ITU on 30 patients with an indication for operative forceps delivery. Managing obstetricians were blinded to the results. ITU was performed just before blade application, between contractions and concurrently with contractions and active pushing. Forceps delivery was classified as complicated when one or more of the following situations occurred: three or more tractions; a subjective impression of a difficult or failed application; a third-degree or higher perineal tear; significant bleeding during the episiotomy repair; major tear; significant traumatic neonatal lesion.


Twenty-one forceps deliveries were classified as uncomplicated and nine were complicated. The strongest predictor of a complicated forceps delivery, calculated using the area under the receiver–operating characteristics curve (AUC), was the AOP between contractions (AOP1) (AUC = 98.9%). The best cut-off for predicting a difficult forceps delivery was an AOP1 of 138° (sensitivity = 85.7%, specificity = 100%). The best predictive model included both the AOP1 and the HD during a contraction with active pushing (HD2).


The sonographic parameters AOP and HD can be used to predict complicated operative forceps delivery in fetuses in non-occiput posterior position. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.