This infant is macrosomic, suffered from shoulder dystocia during delivery, and now has an asymmetric Moro reflex with “waiter’s tip” arm positioning, most likely Erb’s palsy due to brachial plexus injury. Shoulder dystocia and consequent Erb’s palsy can be prevented by strict glycemic control during pregnancy, as this decreases the risk of macrosomia.
Gestational diabetes is a major cause of macrosomia, which is defined as fetal weight > 4500 g for diabetic patients such as this one. This infant’s mother had abnormal glucose tolerance tests that established a diagnosis of gestational diabetes, and despite insulin therapy, had postprandial glucose levels that were well above the cutoff of 140 mg/dL. Her glycemic control was clearly poor during pregnancy, which is the strongest risk factor for macrosomia and shoulder dystocia. Induction of labor at 39 weeks is often recommended if estimated fetal weight is high, and vaginal delivery is acceptable although prophylactic C-section is sometimes considered. This patient’s delivery is classic for shoulder dystocia. The infant’s head was delivered but the torso was not, since the head-to-shoulder ratio is lower in macrosomic infants of diabetic mothers. Erb’s palsy is the most common such injury from shoulder dystocia and is a result of damage to the C5-6 nerve roots. “Waiter’s tip” positioning with an extended forearm and flexed wrist may be seen, and the Moro startle reflex will be absent on the same side. Neurologic damage can be transient or permanent for these infants.
Figure A shows an infant with Erb's palsy on the left side with "waiter's tip" positioning.
Answer 1: Operative vaginal delivery with forceps or vacuum is sometimes used when expedient delivery is necessary due to fetal or maternal distress. However, it has not been shown to be especially useful in resolving shoulder dystocias and may even increase the risk of neurological damage from delivery in these cases.
Answer 2: Administration of magnesium sulfate can be used as a tocolytic before 34 weeks gestation, for neuroprotection against cerebral palsy if delivery is likely before 32 weeks gestation, or for preeclampsia to prevent maternal seizure. Although cerebral palsy may cause neurological symptoms such as spasms, contractures, and hypertonicity, it generally would not present similarly to Erb’s palsy as in this infant. Magnesium sulfate would therefore not have been useful for preventing this presentation.
Answer 3: Decreased caloric intake in the mother during pregnancy would decrease the risk of maternal obesity and associated complications such as preeclampsia, intrauterine fetal demise, and congenital anomalies. However, there is no clear link between maternal obesity and fetal macrosomia or shoulder dystocia. Furthermore, this mother had an appropriate weight gain between 25-40 pounds and a normal prepregnancy BMI.
Answer 5: Episiotomy involves incision of the perineum during delivery. Although it is occasionally performed in shoulder dystocias to allow additional room for internal rotation, it is not generally indicated to facilitate delivery unless internal rotation is unsuccessful. In this case, internal rotation was performed even without episiotomy, making this intervention unlikely to have changed the outcome.
Maternal hyperglycemia in pregnancy is strongly associated with macrosomia, which may lead to shoulder dystocia at the time of delivery. Erb’s Palsy is the most common neurologic consequence of this and may result in either temporary or permanent damage.