A 2-hour-old boy is evaluated in the newborn nursery due to an asymmetric Moro reflex. The infant was born via vaginal delivery to a 32-year-old woman, gravida 3 para 3. Labor was induced at 39 weeks gestation due to oligohydramnios noted on prenatal ultrasound. The mother received 5 doses of penicillin during labor for a positive test for group B Streptococcus. Labor was prolonged and required vacuum assistance due to difficult extraction. The pregnancy was complicated by gestational diabetes mellitus, which was not well controlled. The fetal lie was breech at 18 and 27 weeks gestation but was cephalic starting at 30 weeks. The infant weighs 4.6 kg (10 lb 3 oz, 99th percentile). Finger-stick glucose was 39 mg/dL at birth and increased to 54 mg/dL after formula. The infant is sleeping but wakes during examination and cries. A large cephalohematoma is noted at the vacuum site. Cardiopulmonary examination is normal. The right arm is adducted and internally rotated and the forearm is pronated at rest. When the Moro reflex is elicited, the right arm has decreased movement. The palmar grasp reflex is present in both hands. Which of the following risk factors likely contributed to this patient's abnormal neurologic findings?

Question

A 2-hour-old boy is evaluated in the newborn nursery due to an asymmetric Moro reflex.  The infant was born via vaginal delivery to a 32-year-old woman, gravida 3 para 3.  Labor was induced at 39 weeks gestation due to oligohydramnios noted on prenatal ultrasound.  The mother received 5 doses of penicillin during labor for a positive test for group B Streptococcus.  Labor was prolonged and required vacuum assistance due to difficult extraction.  The pregnancy was complicated by gestational diabetes mellitus, which was not well controlled.  The fetal lie was breech at 18 and 27 weeks gestation but was cephalic starting at 30 weeks.  The infant weighs 4.6 kg (10 lb 3 oz, 99th percentile).  Finger-stick glucose was 39 mg/dL at birth and increased to 54 mg/dL after formula.  The infant is sleeping but wakes during examination and cries.  A large cephalohematoma is noted at the vacuum site.  Cardiopulmonary examination is normal.  The right arm is adducted and internally rotated and the forearm is pronated at rest.  When the Moro reflex is elicited, the right arm has decreased movement.  The palmar grasp reflex is present in both hands.  Which of the following risk factors likely contributed to this patient's abnormal neurologic findings?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c02e_b73d_8f63_8bea0c25f77c_MD0005_00 This child has adduction and internal rotation of the upper extremity, a pronated forearm, and an asymmetric Moro reflex. These findings are characteristic of Erb-Duchenne palsy (or Erb palsy), a brachial plexus injury involving nerves C5-C7. Brachial plexus injuries in newborns are most commonly caused by stretching of the plexus (eg, significant neck traction) during delivery. Infants with difficult extraction (eg, shoulder dystocia, forceps- or vacuum-assistance) often experience more traction and force and are at higher risk for Erb-Duchenne palsy. Macrosomia (birth weight >4 kg [8 lb 8 oz]), often seen in gestational diabetes, is a major risk factor for shoulder dystocia and therefore brachial plexus injuries. Brachial plexus injuries also occur in infants without risk factors, presumably because an uncomplicated labor and delivery also requires some neck traction. Diagnosis is clinical, and most cases spontaneously improve over weeks to months. (Choice A) Breech positioning can be associated with deformational changes in the fetus and newborn, including torticollis and developmental dysplasia of the hip. However, it is not associated with an increased risk for brachial plexus injury. (Choice B) Infants whose mothers have diabetes or who are macrosomic are at increased risk of hypoglycemia, which can present with jitteriness or irritability. Hypoglycemia is not related to brachial plexus injury. (Choice D) Oligohydramnios may be isolated or associated with other pregnancy complications (eg, growth restriction, preeclampsia). If the oligohydramnios is severe or prolonged, neonates may have pulmonary hypoplasia, flattened facies, and limb deformity (eg, clubfoot). There is no association with brachial plexus injury. (Choice E) Prolonged (>18 hours) rupture of membranes increases the risk of chorioamnionitis and neonatal sepsis. Newborns with sepsis may appear ill and have temperature instability. This condition does not increase the risk of brachial plexus injury. Educational objective: Neonatal brachial plexus injuries (eg, Erb-Duchenne palsy) are most commonly associated with shoulder dystocia in macrosomic infants. Most infants recover spontaneously with supportive care. References: Risk factors for neonatal brachial plexus injury. (http://www.ncbi.nlm.nih.gov/pubmed/24863028)

A 2-Hour-Old Boy Is Evaluated in the Newborn Nursery Due