McRoberts Maneuver

Anatomy and Physiology

When assessing the need for McRobert’s Maneuver, the structure of the female pelvis becomes of primary importance.  Four bones compose the pelvis: Sacrum, coccyx, and the two innominate bones. The ilium, ischium, and pubic rami fuse to form the innominate bones.[3]

Within the pelvis, there are three joints: two sacroiliac joints posteriorly, and the pubic symphysis anteriorly.  The pelvic type depends upon the manner in which the bones of the pelvis fuse.  The "Caldwell-Moloy" classification system has classified four basic pelvis shapes: Gynecoid, anthropoid, android, and platypelloid.  A transverse line at the greatest diameter of the pelvic inlet determines the pelvic type.  This transverse line separates the anterior and posterior portions of the pelvis.  The majority of patients have a gynecoid shaped pelvis with almost equal anterior and posterior regions. This creates the largest internal space, compared to the other pelvis shapes, and helps facilitate the delivery of the fetus.  Pelvic shapes that contain a decreased anterior to posterior diameter may increase the chance of shoulder dystocia and decreased likelihood of a normal descent of the fetus.[4]

When defining the anterior-posterior diameter, also known as the conjugate, one must consider the confines of the pelvic inlet. The pubic symphysis anteriorly, the sacral promontory posteriorly, and the linea terminalis laterally altogether confine the pelvic inlet. The distance to the sacral promontory from the inferior margin of the pubic symphysis determines the diagonal conjugate. The obstetrical conjugate is the diagonal conjugate minus 1-2cm.

Indications

While there are no specific indicators for the use of McRobert's maneuver, there are several antepartum and intrapartum conditions that can place a patient at a higher risk of developing shoulder dystocia. Antepartum conditions include diabetes, previous large birthweight infant, increased maternal weight gain, and maternal obesity.[5] Intrapartum conditions that may signal the possibility of shoulder dystocia include a prolonged second stage and failure of descent of the fetal vertex.

No advantage has been observed with performing prophylactic McRobert's maneuver prior to shoulder dystocia diagnosis, however, there are minimal to no disadvantages in using the maneuver prophylactically.[6]

Contraindications

There are no documented contraindications to the use of the McRobert’s maneuver in patients who have no known hip or pelvic-related deformities.

Equipment

There is no specific equipment needed for performing the McRobert’s maneuver.  The McRobert's maneuver is performed by two people simultaneously.  Two stools should be available on either side of the patient's bed for the labor room personnel.  An assistant may also help aid in the performance of suprapubic pressure if performed along with McRobert's maneuver.

Preparation

There is little preparation needed when performing the McRobert’s maneuver. Before delivering the patient with a suspicion of dystocia, a briefing with all labor room personnel should occur. This briefing should take place for all patients whose obstetrical risk factors include maternal obesity, large for gestational age, post-date pregnancy, etc.  The briefing should include nursing staff, obstetricians, anesthesiologists, and pediatricians.  The goal is to have all personnel who are caring for the patient be aware of the patient’s personal risk factors.  

One measurement that proves helpful in identifying patients at risk for dystocia is the shoulder dystocia risk measurement.  This assessment is performed after a bedside sonogram. Measurements of the abdominal circumference (AC) and head circumference (HC) are taken. The shoulder dystocia risk measurement is as follows: (AC/pi) – HC. The number pi is usually rounded and represented as 3.14. A patient is at a statistically increased risk if the result is greater than 2.6.[7]  If the shoulder dystocia risk measurement is positive, a practitioner should not hesitate to perform the McRobert’s maneuver.

Technique or Treatment

Performing the McRobert’s technique requires two personnel positioned at each leg of the patient. The assistants grab and push the maternal feet cephalad — this action results in hyperflexion of the maternal hips and knees onto along with slight hip abduction resulting in the superior displacement of the pubic symphysis by 1-2 cm.  McRobert’s maneuver also results in sacral extension or counter-nutation.  As the sacrum moves posteriorly, the angle created between L5 and the sacral promontory flattens and becomes wider.  As the sacral promontory flattens, the posterior shoulder of the fetus moves posteriorly and inferiorly into the pelvis.  This positional change subsequently allows the anterior shoulder to move from under the pubic symphysis facilitating delivery.  The flattening of the sacral promontory simultaneously enables the force produced by spontaneous uterine contractions and maternal pushing efforts to be more effective.[8][9]

Complications

There is little documentation on the complications of McRobert’s maneuver in the current literature. However, there are several reported cases which highlight the possible complications which may arise.  One potential complication is that of lower extremity neuropathy. Lower extremity neuropathy results from prolonged compression of the femoral nerve beneath the inguinal ligament, which can lead to decreased hip flexion and knee extension on the ipsilateral side of the injury.  Another complication which may arise is symphyseal separation.  This complication results from excessive abduction of the hips. The literature notes surgical management with internal fixation was necessary. The last documented complication of McRobert’s maneuver involved a case of sacroiliac joint dislocation.  The resolution of the dislocation required using closed reduction by an orthopedic team.  These complications were all cited with excessive time spent performing the McRobert’s technique.[10]

Enhancing Healthcare Team Outcomes

The safe and effective performance of the McRobert's maneuver requires two people. Each person should take a position at each leg of the patient — capable, trained obstetrical personnel aid in the performance of the McRobert’s maneuver.  Obstetrical personnel should be knowledgeable of other techniques which resolve shoulder dystocia.