The McRoberts maneuver is an obstetric technique used during childbirth to address a specific complication. It involves precise positioning of the birthing person’s legs and hips to facilitate the baby’s safe passage during vaginal delivery.
Understanding Shoulder Dystocia
Shoulder dystocia is a complication during vaginal delivery where, after the baby’s head emerges, one or both shoulders become lodged behind the mother’s pubic bone. This condition occurs in approximately 0.6% to 1.4% of vaginal births for average-sized babies, with the rate increasing to 5% to 9% for larger infants over 8 pounds, 13 ounces. While often unpredictable, factors like a large baby, maternal diabetes, or a small pelvis can increase its likelihood.
Shoulder dystocia poses risks to both baby and mother. For the baby, prolonged impaction can lead to oxygen deprivation, potentially causing hypoxic-ischemic encephalopathy. Physical injuries, including brachial plexus nerve damage or collarbone/upper arm fractures, are also possible. Mothers may experience severe vaginal or cervical lacerations, increased blood loss, or, rarely, uterine rupture.
Performing the McRoberts Maneuver
The McRoberts maneuver is a physical technique to resolve shoulder dystocia. It involves hyperflexing the birthing person’s legs sharply back towards their abdomen, bringing the knees up towards the chest. One or two assistants perform this action, holding each leg and pushing it firmly back.
This positioning changes the angle of the pelvis, creating more space for the baby to pass. It is a rapid and initial intervention, as time is crucial during shoulder dystocia. The maneuver is safe and does not involve internal manipulation of the baby.
How the Maneuver Aids Delivery
The McRoberts maneuver’s effectiveness stems from its biomechanical impact on the maternal pelvis. Hyperflexing the thighs onto the abdomen causes the sacrum, the triangular bone at the base of the spine, to straighten relative to the lumbar spine. This straightening also leads to a cephalad, or upward, rotation of the maternal symphysis pubis, the joint connecting the two halves of the pelvis at the front.
These anatomical changes do not increase the physical dimensions of the pelvis, but rather alter its orientation. The pelvis’s rotation effectively increases the functional diameter of the pelvic outlet. This subtle shift in pelvic alignment can be sufficient to dislodge the impacted shoulder, allowing delivery.
Outcomes and Further Steps
The McRoberts maneuver is an effective initial intervention for shoulder dystocia. Performed alone, it resolves impaction in approximately 39% to 42% of cases. Its success rate increases, ranging from 54% to 90%, when combined with suprapubic pressure, where an assistant applies external pressure to the mother’s lower abdomen above the pubic bone.
Should the McRoberts maneuver, even with suprapubic pressure, not resolve shoulder dystocia, providers proceed with other sequential maneuvers. These may include rotational techniques, such as the Woods screw or Rubin maneuver, or delivery of the posterior arm. These approaches aim to create additional space or change the baby’s position, prioritizing swift and safe emergency resolution.