What I found for the question is that due to -
Oligohydramnios reduces the intrathoracic cavity size, thus disrupting fetal lung growth and leading to pulmonary hypoplasia.
decreased fetal breathing movements, and
decreased extrinsic stretch due to fluid in alveoli leads to hypoplasia of lung.here
I get the the decreased extrinsic stretch part but how come fetal breathing movements decrease with oligohydramnios? Is it because friction increases or something else?
Secondly, how oligohydramnios leads to decreased intrathoracic size? Is it because less fluid is swallowed in or something else is in play?