Randomized trial of McRoberts versus lithotomy positioning to decrease the force that is applied to the fetus during delivery

In an effort to reduce shoulder dystocia incidence and morbidity, some obstetricians use prophylactic maternal hip hyperflexion (McRoberts maneuver), with the hope of facilitating delivery and decreasing the traction needed for delivery. The objective of this study was to evaluate whether the delivery force is reduced with the prophylactic McRoberts maneuver in a prospective, objective manner. Between April 2002 and July 2003, we randomly assigned multiparous women with term, cephalic singleton gestations to delivery in the lithotomy or McRoberts position. A single physician used a force-measuring system that consisted of a custom glove with force sensors to record the amount of force that was exerted on the fetal head. The primary outcomes of the study were peak force (pounds; highest force needed to accomplish entire delivery), peak force for delivery of anterior shoulder (pounds), and peak force rate (pounds per second; the duration required to reach the peak force). The peak force was not different between the patients in the lithotomy position (n=13) versus the McRoberts position (n=14; 7.2 ± 0.8 lbs vs 8.0 ± 0.7 lbs; P = .5). The peak force for delivery of the anterior shoulder (6.7 ± 0.8 lbs vs 7.1 ± 0.7 lbs; P = .7) and peak force rate (32.3 ± 7.0 lbs/sec vs 29.1 ± 3.5 lbs/sec; P = .7) were not different between the patients in the lithotomy position versus the McRoberts position, respectively. There was no difference between the groups for gestational age, birth weight, incidence of diabetes mellitus, or operative vaginal delivery. The subjective degree of difficulty of the delivery correlated with the peak force ( R 2 = 0.53; P = .001). The use of the McRoberts maneuver before clinical diagnosis of shoulder dystocia provides no reduction in the force that is used in traction on the fetal head during vaginal delivery in multiparous patients. The acceptance of this maneuver to be used prophylactically requires re-evaluation.