In the layers of the bladder wall are a mucosa layer that has a transitional epithelium, which is stretchy and allows the bladder to distend while maintaining a barrier between urine and the body.
Preemies' lungs haven't yet developed enough of these surfactants, so the small alveoli squeeze too much and collapse, while the larger ones keep blowing up and get distended.
For the next few hours, as my stomach grows distended from the food, it activates stretch receptors that again stimulate my medulla and get my vagus nerves to tell my stomach to turn up the juice.
One common manifestation of this is jugular venous distention, where the jugular vein that brings blood back to the heart takes on more blood and becomes enlarged and distended in the neck.
Anything that over distends the uterus, so multiple gestation, polyhydramnios, macrosomic baby, hypertension is a risk factor, and then of course any type of coagulopathy.