Pearls on the McRoberts maneuver

This procedure does not change the actual dimensions of the maternal pelvis.

A lthough shoulder dystocia occurs in less than 1% of all births, it can lead to serious injury of the infant and mother. Potential fetal complications include death, permanent neurologic impairment, brachial plexus injury, and Erb’s palsy, while the mother may suffer vaginal and cervical lacerations, significant blood loss, or uterine rupture.

Several techniques can be administered to safely dislodge the infant’s shoulder, including the Woods-screw, Rubin, Gaskin (“all-fours”), and McRoberts maneuvers. I prefer the Mc-Roberts maneuver because it involves only maternal manipulation while allowing the fetal shoulder to rotate into the oblique diameter.

Success rates. McRoberts is not only technically simple to employ, but has been found to alleviate 39% to 42% of shoulder dystocias when used alone.¹ The addition of suprapubic pressure and/or proctoepisiotomy increases success rates to between 54% and 58%.^1,2 In patients with diabetes, however, success rates are not higher.¹ This is most likely due to the fact that infants of mothers with diabetes tend to have higher birthweights than infants of gravidas without the disease.

Prophylaxis. To date, no clinical studies have evaluated birth outcomes after the prophylactic employment of the McRoberts maneuver, even though the procedure is commonplace. Since McRoberts has many potential benefits (Table 1), it is reasonable to consider its prophylactic use in suspected fetal macrosomia or when concern for shoulder dystocia exists. The maneuver also may be useful in managing an entrapped fetal head during a vaginal breech delivery.³

Mechanism of action. Contrary to popular belief, the McRoberts maneuver does not change the actual dimensions of the maternal pelvis. In a recently published x-ray pelvimetry analysis, we found no significant changes in the anterior-posterior and transverse diameters of the pelvic inlet, midpelvis, and pelvic outlet.⁴ Nor did the obstetric, true, and diagonal conjugates increase when McRoberts was applied. Our analysis thus confirms Gonik’s hypothesis that McRoberts relieves shoulder dystocia via marked cephalad rotation of the symphysis pubis and flattening of the sacrum.⁵

The maneuver also may work by converting voluntary maternal expulsive effort, independent of uterine contractions, into enhanced intrauterine pressure. Buhimschi and colleagues found that McRoberts not only increased the intrauterine pressure during the second stage of labor by 97%, but also increased the amplitude of uterine contractions.⁶ Further, they calculated that McRoberts added 31 N of pushing force when employed during delivery.

Technical considerations. The technique is performed by flexing the mother’s thighs toward her shoulders while she is lying on her back. No specific degree of elevation or flexion of the patient’s legs has been defined for the McRoberts maneuver. Recent obstetric textbooks simply state that McRoberts is performed by “hyperflexing” or “sharply flexing” the maternal legs on the abdomen.^7,8

The overwhelming majority of patients can assume the proper position for the McRoberts maneuver with little difficulty. Women may be instructed to grasp the posterior aspect of their thighs and pull themselves into position, with family members or health-care professionals providing any assistance necessary. The obstetrician also may choose to flex both of the patient’s legs.

Problems may occur when moving an obese patient or a woman who has undergone a dense epidural motor blockade. Further, patients with pelvic fractures, spinal-cord injuries, severe degenerative joint disorders (osteoarthritis or rheumatoid arthritis), or neuromuscular disorders may have trouble assuming a dorsal lithotomy position, making the McRoberts maneuver difficult or impossible to perform.

Additional maneuvers. My colleagues and I have found that the need for additional maneuvers after McRoberts has been performed is correlated to fetal birthweights, length of the active phase of labor, and length of the second stage of labor.¹ In these circumstances, additional maneuvers including suprapubic pressure, fetal rotational maneuvers (Woods or Rubin), extraction of the posterior fetal arm, and proctoepisiotomy may be employed. I recommend that the patient undergo the McRoberts maneuver while these ancillary techniques are performed. Since these techniques involve direct fetal manipulation, they should not be hindered by McRoberts.

Neonatal injury. The McRoberts maneuver does not remove the inherent risk of neonatal bone or nerve injury associated with shoulder dystocia. Even among patients who undergo McRoberts only, approximately 10.2% of infants will have brachial plexus injuries.¹