[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Respiratory system, diaphragm and body cavities](https://durgical.com/en/embryology/#a-respiratory) › Pulmonary hypoplasia [Embryology](https://durgical.com/en/embryology/) · [Respiratory system, diaphragm and body cavities](https://durgical.com/en/embryology/#a-respiratory) # Pulmonary hypoplasia - Malformation The lungs end up small, with few branches and air sacs, because something took away their room or their fluid during pregnancy. Updated 2026-11-01 **See it in 3D:** [Main bronchi](https://durgical.com/en/anatomy/right-main-bronchus/) · [Pulmonary arteries](https://durgical.com/en/anatomy/right-pulmonary-artery/) · [Kidneys](https://durgical.com/en/anatomy/kidney/) ## Key points - Three mechanisms: chest compression, oligohydramnios and absent fetal breathing movements. - Congenital diaphragmatic hernia: the commonest cause by compression. - Bilateral renal agenesis or posterior urethral valves: oligohydramnios and the Potter sequence. - Very early, prolonged rupture of membranes before week 24. - Critical window: pseudoglandular and canalicular stages (weeks 5 to 26). - Comes with pulmonary hypertension from a reduced vascular bed. ## What it is Pulmonary hypoplasia is a lung with fewer cells, airways, alveoli and vessels than normal. It is nearly always secondary: too little room in the chest, too little amniotic fluid or too few fetal breathing movements during the second trimester. It is the main cause of death in congenital diaphragmatic hernia and in the Potter sequence. ## Embryological cause - The fetal lung needs room, fluid in the airways and breathing movements to branch. - Compression: diaphragmatic hernia, pleural effusion, hydrops or a small chest from skeletal dysplasias. - Oligohydramnios: without fluid the chest is squeezed and lung fluid escapes, which stalls growth. - Absent breathing movements: neuromuscular or fetal nervous system disease. - If the insult falls in the pseudoglandular and canalicular stages, fewer bronchial generations, alveoli and vessels form. ## How it presents - Severe respiratory failure from birth, with a small chest. - Spontaneous pneumothorax or pneumothorax during ventilation. - Persistent pulmonary hypertension of the newborn. - In the Potter sequence: flattened face, low-set ears and limb deformities. ## Diagnosis - Prenatal: low lung-to-head ratio on ultrasound and reduced lung volume on fetal MRI. - X-ray: small chest and poorly expanded lungs. - Autopsy: low lung weight relative to body weight and a reduced radial alveolar count. ## Memory aid The fetal lung grows on three things: room, water and breathing practice. Take one away in the second trimester and it stays small. ## Test yourself Think of the answer, then tap the question to see it. ## What are the three main mechanisms of pulmonary hypoplasia? Chest compression (for example diaphragmatic hernia), oligohydramnios and absent fetal breathing movements. ## In which stages of lung development is the lung most vulnerable to hypoplasia? The pseudoglandular and canalicular stages, weeks 5 to 26, when bronchial branches and vessels form. ## Why does bilateral renal agenesis cause pulmonary hypoplasia? Because with no fetal urine there is severe oligohydramnios; the chest is compressed and the lung loses the fluid it needs to grow. ## Which vascular complication comes with pulmonary hypoplasia? Persistent pulmonary hypertension, because the lung's vascular bed is small. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/pulmonary-hypoplasia/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Main bronchi](https://durgical.com/en/anatomy/right-main-bronchus/) - [Pulmonary arteries](https://durgical.com/en/anatomy/right-pulmonary-artery/) - [Kidneys](https://durgical.com/en/anatomy/kidney/) ## Related - [Congenital diaphragmatic hernia](https://durgical.com/en/embryology/congenital-diaphragmatic-hernia/) - [Renal agenesis and the Potter sequence](https://durgical.com/en/embryology/renal-agenesis-and-the-potter-sequence/) - [Amniotic fluid: polyhydramnios and oligohydramnios](https://durgical.com/en/embryology/amniotic-fluid-polyhydramnios-and-oligohydramnios/) - [Lung development: the five stages](https://durgical.com/en/embryology/lung-development-the-five-stages/) - [Duplicated ureter, UPJ obstruction and posterior urethral valves](https://durgical.com/en/embryology/duplicated-ureter-upj-obstruction-and-posterior-urethral-valves/) - [Malformation, disruption, deformation, sequence, syndrome, association](https://durgical.com/en/embryology/malformation-disruption-deformation-sequence-syndrome-association/) ## Related conditions - [Premature rupture of membranes (PROM and PPROM)](https://durgical.com/en/conditions/premature-rupture-of-membranes/) - [Pulmonary hypertension and cor pulmonale](https://durgical.com/en/conditions/pulmonary-hypertension-and-cor-pulmonale/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Potter syndrome: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001268.htm) (MedlinePlus, U.S. National Library of Medicine, 2025); [Congenital diaphragmatic hernia: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/congenital-diaphragmatic-hernia) (MedlinePlus, U.S. National Library of Medicine, 2019); Langman's Medical Embryology, 13th ed., ch. 14: Respiratory System (Wolters Kluwer, 2015). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/pulmonary-hypoplasia/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/pulmonary-hypoplasia/