**3.1. Definition and incidence**

Bronchopulmonary sequestration (BPS) represents a cystic mass of nonfunctioning pulmonary tissue with the blood supply from the systemic vessels and not from the pulmonary arteries.

The incidence reported is 0.5–6.0% of all prenatally diagnosed pulmonary lesions [16].

Pulmonary sequestration can be: intrapulmonary and extrapulmonary. Intrapulmonary sequestration (IPS) represents almost 75% of the cases, but this form is rarely diagnosed in utero. The abnormal lung tissue lies within the normal lung tissue. This variety is produced by the bronchial obstruction.

Extrapulmonary sequestration (EPS) is the most commonly form diagnosed in the prenatal life. The abnormal lung tissue has its own pleural covering, so the abnormal pulmonary tissue is separated from the normal pulmonary tissue and the pathologic tissue drains in the systemic circulation. The extrapulmonary sequestration is considered to be an abnormal pulmonary tissue that has no connection with the bronchial tree. The vascularization is provided by arteries emerging from the aorta.
