21. Dystocia caused by abnormalities of fetal structure or maternal pelvic alterations

Question 1

how is macrosomia defined?

Answer 1

birth weight > 4000-4500 g

Question 2

Large for Gestational Age (LGA) is defined as?

Answer 2

estimated fetal weight > 90th percentile

Question 3

comorbidities associated with marcosomia?

Answer 3

• Labor dystocia
• Shoulder dystocia
• Low Apgar score
• Neonatal hypoglycemia
• Maternal genital trauma
• Cesarean delivery (risk ↑)
• Postpartum hemorrhage (risk ↑)
• Puerperal infection (risk ↑)

Question 4

Management of LGA and macrosomic infants includes?

Answer 4

prevention, surveillance, and induction of labor before the attainment of macrosomia.

Question 5

when is LGA or macrosomia detected?

Answer 5

1. during routine prenatal care on the basis of size/date discrepancy.
2. US evaluation of biparietal diameter, femur length, and abdominal circumference provides fetal weight estimation with accuracy of around 10-15%.

Question 6

what is shoulder dystocia?

Answer 6

Obstetric emergency in which the anterior shoulder of the fetus is impacted behind the maternal pubic symphysis

Question 7

risk factors for shoulder dystocia

Answer 7

macrosomia, gestational diabetes, previous shoulder dystocia, maternal obesity, post-term pregnancy, prolonged second stage of labor, and operative vaginal delivery

Question 8

Comorbidities associated with shoulder dystocia?

Answer 8

-Erb palsy → brachial plexus nerve injury affecting the upper trunk (C5-C6 nerve roots).
-Fractures of the humerus and clavicle.
-Phrenic nerve palsy.
-Hypoxic brain injury.
-Fetal death.

Question 9

what nerves are involved in Erb palsy and how does it manifest?

Answer 9

Nerves involved include the suprascapular, musculocutaneous, and axillary
manifests with an adducted, extended, pronated, and medially rotated arm (‘waiter’s tip position’).

Question 10

risk factors for macrosomia

Answer 10

genetic determinants, maternal diabetes, maternal obesity (BMI > 30), excessive weight gain during pregnancy, multiparity, male infant, postterm pregnancy, advanced maternal age, Beckwith-Wiedemann syndrome (pancreatic islet cell hyperplasia).

Question 11

when is Diagnosis of shoulder dystocia made?

Answer 11

when routine obstetric maneuvers fail to deliver the fetus
Suspicion is increased when the fetal head retracts into the perineum after expulsion (‘turtle sign’)
goes out and then in

Question 12

what 1st line Maneuvers are used for delivering an infant with shoulder dystocia?

Answer 12

McRoberts maneuver
Suprapubic pressure

Question 13

how is McRoberts maneuver done?

Answer 13

Sharp flexion of the maternal hips decreases the inclination of the pelvis, increasing the AP diameter.

Question 14

how is suprapubic pressure done?

Answer 14

Pressure is applied just above the maternal pubic symphysis at an oblique angle to dislodge the anterior shoulder.

Question 15

what 2nd line Maneuvers are used for delivering an infant with shoulder dystocia?

Answer 15

1. Rubin maneuver
   2.Wood’s corkscrew maneuver
   3.Delivery of the posterior arm/shoulder

Question 16

how is Rubin maneuver done?

Answer 16

Pressure is applied behind the posterior shoulder to cause anterior rotation toward the fetal face. The shoulders are displaced from the anteroposterior diameter of the inlet, thereby allowing the posterior arm to enter the pelvis.

Question 17

how is Wood’s corkscrew maneuver done?

Answer 17

Rotate the fetus by exerting pressure on the anterior surface of the posterior
shoulder, turn the fetus until the anterior shoulder emerges from behind the pubic.

Question 18

how do we Deliver the posterior arm/shoulder?

Answer 18

Deliver the arm from a flexed elbow position.
Alternatively, apply axial traction to deliver the posterior shoulder.

Question 19

last-resort procedures for shoulder dystocia

Answer 19

1.Fracture the clavicle
2.Zavanelli maneuver
3.Symphysiotomy

Question 20

what is done in Symphysiotomy?

Answer 20

Surgical division of the cartilage of the symphysis pubis; allows the pubic bones to
separate, thereby increasing the size of the pelvic opening and relieving the
obstruction to delivery.

Question 21

Zavanelli maneuver

Answer 21

Administer a tocolytic agent → push back the fetal head into the pelvis → perform emergency cesarean delivery.