A 35-year-old pregnant woman, has gone into labor at 39 week

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You are notified that one of your patients, a 35-year-old pregnant woman, has gone into labor at 39 weeks. By the time you arrive at the hospital, the baby has already been born during an uneventful delivery, about 2 minutes earlier. You go to examine the baby on the warmer and discover that he has respiratory distress and is becoming cyanotic. You attempt to oxygenate him with a mask, but this does not seem to provide him with much relief. Physical examination shows subcostal and intercostal retractions, absent air entry on the left side, poor air entry on the right side, and "gurgle-like" sounds in the left chest. The heart sounds are best heard in the right hemithorax; the abdomen is flat without organomegaly. The most likely cause of these findings is

A. aspiration of meconium at delivery
B. a defect in the left hemidiaphragm
C. a deficiency of surfactant
D. dextrocardia and situs inversus
E. esophageal atresia with distal tracheoesophageal fistula
F. transposition of the aorta and pulmonary artery

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The answer is B. This patient most likely has a congenital diaphragmatic hernia, which is when the abdominal contents herniate into the left hemithorax through a congenital defect in the left hemidiaphragm. This causes displacement of the heart into the right hemithorax and pulmonary hypoplasia. If gas has entered the bowel tract, bowel sounds (gurgle-like noises) can be heard in the chest. The displacement of the abdominal contents renders the abdomen flat. In cases of severe pulmonary hypoplasia, administration of oxygen results in only a poor improvement in oxygenation.

Meconium aspiration (choice A) should be accompanied by a history of fetal stress, meconium stained amniotic fluid, or meconium staining of the skin, placenta, or umbilical cord. Physical findings are symmetric, with no displacement of the heart, the breath sounds should be similar on both sides, and there should not be bowel sounds in the chest.

Hyaline membrane disease is caused by a deficiency of surfactant (choice C) and is a rare condition in an infant born at 39 weeks. It typically occurs in infants born before 32 weeks, when surfactant is produced. Surfactant is a phospholipid that prevents alveolar collapse by increasing lung compliance and decreasing surface tension.

It is very unlikely that this patient has dextrocardia and situs inversus (choice D), which are rare positional anomalies where the apex of the heart is on the right (instead of the left) and the abdominal viscera are reversed (the liver is on the left and the stomach is on the right). In cases of dextrocardia and situs inversus, the breath sounds should be basically normal on both sides, and you should not be able to hear bowel sounds in the chest.

Esophageal atresia with distal tracheoesophageal fistula (choice E) usually presents with a history of polyhydramnios, cyanosis with feeding, and increased oropharyngeal secretions. It is unusual for this condition to present so soon after birth with severe respiratory distress.

Transposition of the aorta and pulmonary artery (choice F) is a rare form of congenital heart disease where the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. Infants with this disorder are cyanotic from birth and congestive heart failure usually follows. However the breath sounds would be similar on both sides and there would not be bowel sounds in the chest.