If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.
This month’s stumper
A 34-year-old G1P0 woman at 39 weeks presents for rupture of membranes. The patient felt a gush of fluid one-hour ago, denies vaginal bleeding and is feeling contractions every three to four minutes. She feels the baby moving.
The patient's prenatal course has been complicated by gestational diabetes for which she is following a special diet but no medication. She progressed to fully dilated and began pushing 90 minutes ago. The fetal head was delivered 30 seconds ago, and anterior shoulder has not been able to be delivered. The nurses are applying suprapubic pressure.
Which of the following is the next step in the management of this patient?
A. Caesarean section.
B. Clavicular fracture.
C. Delivery of posterior shoulder.
D. McRoberts maneuver.
E. Zavanelli maneuver.
The correct answer is D.
Kaplan Medical explains why
The patient is experiencing a shoulder dystocia. Shoulder dystocia is a common complication of gestational diabetes and occurs when the anterior shoulder cannot be delivered. The anterior shoulder is "stuck" behind the pubic symphysis, which can be life-threatening for both the fetus and the mother.
Shoulder dystocia is an intrapartum diagnosis made when gentle downward traction of the head does not release the anterior shoulder from behind the pubic symphysis. A "turtle sign" may be noted (fetal head emerges and then seems to retract back into vaginal canal) and can be a warning for shoulder dystocia. Time is of the essence in these situations and the fetus should be delivered as quickly as possible.
The first step in management is suprapubic pressure to push the fetal shoulder below the pubic symphysis. If this does not release the shoulder, place the patient in McRoberts maneuver. McRoberts is considered the least invasive maneuver and includes maternal thigh flexion by assistants. The assistants should flex the thigh against the abdomen. This maneuver will open the pelvis and allow for delivery of the fetus. If this does not work, one should try other maneuvers which can help to rotate the fetus within the vaginal canal to free the shoulder.
Why the other answers are wrong
Choice A: Caesarean section is the last treatment option for patients with shoulder dystocia. There is a high maternal and fetal mortality when Caesarean section for shoulder dystocia is required.
Choice B: Clavicular fracture occurs when the clavicle of the fetus is intentionally fractured to decrease the shoulder width. This will allow for the fetal shoulder to be delivered. This can cause injury to the fetal vasculature and pulmonary structures under the clavicle; however, it should be tried once after less invasive options have failed. If clavicular fracture fails to release the shoulder, Zavanelli maneuver should be attempted. In Zavanelli, one attempts to replace the fetal head back into the maternal pelvis and an urgent Caesarean is conducted.
Choice C: Delivery of posterior shoulder should be attempted before clavicular fracture. Delivery of the posterior should usually release the dystocia of the anterior shoulder. The physician's hand should be placed into the vagina and the fetal posterior shoulder should be felt. Follow the posterior shoulder down to the elbow and attempt to deliver the fetal arm first. This will drop the posterior shoulder into the pelvis and relieve the dystocia. There is a risk of fracturing the fetal humerus. Patients should undergo the least invasive maneuvers first, and only if they fail should more invasive maneuvers be attempted.
Choice E: Zavanelli maneuver is the replacement of the fetal head back into the maternal pelvis followed by Caesarean delivery. This is the last step in the management of shoulder dystocia. This maneuver should not be attempted first.
Tips to remember
- Shoulder dystocia is a common complication of gestational diabetes but can occur in patients with no risk factors as well.
- It occurs when the anterior shoulder gets stuck behind the pubic symphysis.
- Suprapubic pressure and McRoberts maneuver are the least invasive methods for releasing the anterior shoulder, and are the first steps in the management in shoulder dystocia.
For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.
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