The correct answer is a. CCAM.

A newborn presenting with respiratory distress and a history of polyhydramnios is most likely to have a Congenital Cystic Adenomatoid Malformation (CCAM).

Explanation

• Polyhydramnios is a condition where there is an excessive amount of amniotic fluid in the uterus. This often occurs when the fetus cannot properly swallow or absorb the amniotic fluid.
• CCAM is a non-cancerous lung lesion. A large CCAM can compress the fetus’s esophagus, preventing it from effectively swallowing the amniotic fluid. This leads to an accumulation of fluid, resulting in polyhydramnios. After birth, the mass effect of the CCAM can also compress the normal lung tissue, causing respiratory distress.

Why the other options are less likely:

• b. Right-sided diaphragmatic hernia: While a large diaphragmatic hernia can sometimes cause polyhydramnios, it is less common with right-sided hernias because the liver often prevents a significant portion of abdominal contents from herniating and obstructing the esophagus. The association is stronger with large left-sided hernias.
• c. Congenital lobar emphysema and d. Pulmonary sequestrations: These conditions are not typically associated with polyhydramnios because they do not involve a mass effect that would obstruct the fetus’s ability to swallow amniotic fluid. They are primarily identified after birth due to respiratory distress.

*** Exam Pearl

CCAMs are often detected on an antenatal scan and may be associated with hydrops fetalis. All of the above abnormalities may cause respiratory distress in neonates and infants and large lesions may produce a mediastinal shift. CCAM and sequestrations also being associated with recurrent infection.

Investigations

Chest radiographs show:

• congenital lobar emphysema—hyperinflation of one or more of the pulmonary lobes
• congenital cystic adenomatoid malformations—multicystic, air- filled lesion

Treatment and management

CCAMs diagnosed antenatally are closely monitored as many will resolve or be asymptomatic at birth. If hydrops develops during the pregnancy, thoracoamniotic shunting is indicated and, if respiratory distress occurs, surgical excision is undertaken following delivery. The management of asymptomatic lesions is controversial with some centres recommending excision and others a watch and wait approach. Pulmonary sequestrations and congenital lobar emphysema may be managed conservatively if asymptomatic and resection only performed if complications occur.