The cause of water breaking during pregnancy prematurely is usually unknown for sure.
However it's thought by doctors and medical professionals that the water breaking prematurely which is also known as "PROM" is caused by some infection such as an infection of your Vagina.
Another cause of "PROM" or the water to break prematurely can be too much pressure being put on the amniotic sac due to too much fluid being built up.
Or the baby could also accidentally be putting too much pressure on the membranes of the amniotic sac which could cause the amniotic sac to rupture prematurely which causes your water to break.
If your water breaks too early then the baby could be at risk for infections or lung problems because when a baby is born prematurely or not protected by the amniotic sac then the babies health can suffer.
Babies need to be really full term in the womb and be developed fully before they leave the womb so that they stay safe and healthy.
Premature babies can sometimes survive but it's best to keep the baby in the womb for as long as it's required if possible.
But sometimes the water breaks early and then the baby needs to come out and might need to be put into an artificial womb for further development.