Review Question - QID 217106

This pregnant patient with a history of uncontrolled type 2 diabetes mellitus (hemoglobin A1c of 10.1%) presents in active labor. Her newborn is at risk of neonatal respiratory distress syndrome despite being full-term due to the mother's uncontrolled type 2 diabetes mellitus.

Neonatal respiratory distress syndrome (NRDS) occurs in newborns with immature lungs that are deficient in surfactant. This deficiency in surfactant causes low lung compliance, atelectasis, intrapulmonary shunting, and lung injury. Prematurity is the most common risk factor for NRDS because the lungs of premature infants do not contain sufficient numbers of mature type 2 pneumocytes, which are responsible for producing surfactant. Cesarean delivery can also contribute to the development of NRDS as lack of vaginal compression stress on the infant during delivery causes reduced fetal cortisol production and a resultant reduction in surfactant production. Maternal diabetes also strongly contributes to an increased risk of NRDS. In maternal diabetes, the fetus is exposed to high levels of glucose. High serum glucose in the fetus antagonizes the production of glucocorticoids, leading to delayed development of type 2 pneumocytes, which results in decreased production of surfactant. Signs of NRDS include dyspnea, hypoxia, tachypnea, and severe hypoxemia. NRDS can be prevented by maternal corticosteroid administration or direct administration of surfactant to the infant's lungs. Treatment of NRDS includes respiratory support.

Kawakita et al. reviews the incidence of respiratory morbidity in infants of diabetic parents. They discuss how pregestational diabetes (i.e., type 1 or 2 diabetes existing before pregnancy) contributes to greater neonatal respiratory morbidity than gestational diabetes. They recommend screening and treating diabetes in pregnant patients.

Incorrect Answers:
Answer 1: Polycythemia, rather than anemia, is more likely to occur in infants of diabetic mothers. Polycythemia in these patients is thought to occur due to relative intrauterine hypoxia. Patients will present with diffuse cutaneous erythema that can be seen on physical exam.

Answer 2: Hypocalcemia, rather than hypercalcemia, is more likely to occur in infants of diabetic mothers. The exact mechanism of this association is unclear, though some speculate that the high insulin state of gestational diabetes leads to immaturity of the parathyroid glands. Hypocalcemia presents with increased reflexes and twitching.

Answer 3: Hypoglycemia, rather than hyperglycemia, occurs in infants of diabetic mothers. Due to chronic exposure to high glucose states during pregnancy, newborns will have high circulating insulin at birth. This leads to relative hypoglycemia after birth, during which the newborn is no longer exposed to a high-glucose environment.

Answer 4: High, rather than low, unconjugated bilirubin occurs in infants of diabetic mothers. This may be secondary to immature liver enzymes, as well as polycythemia and high red blood cell turnover. Patients will present with jaundice and may have neurologic deficits.

Bullet Summary:
Maternal diabetes mellitus is a risk factor for neonatal respiratory distress syndrome.