Obstetric brachial plexus palsy: a prospective study on risk factors related to manual assistance during the second stage of labor.

Background: To evaluate the association between obstetric brachial plexus palsy and obstetrical maneuvers during the second stage of delivery.
Methods: Prospective population-based case control study. Cases of obstetric brachial plexus palsy were compared with a randomly selected control group with regard to obstetric management.
Results: Five or more obstetrical maneuvers were used to deliver the infants in 82% in the obstetric brachial plexus palsy group versus 1.8% in the controls. Risk factors independently associated with obstetric brachial plexus palsy were force applied when downward traction was imposed on the fetal head (odds ratio 15.2; 95% confidence interval 8.4-27.7). The incidence of obstetric brachial plexus palsy in the infants in the population was 3.3 per thousand. At 18 months of age 16.1% (incidence of 0.05%) of children had residual functional deficits and downward traction with substantial force was applied in all these cases.
Conclusions: Forceful downward traction applied to the head after the fetal third rotation represents an important risk factor of obstetric brachial plexus palsy in vaginal deliveries in cephalic presentation.