Your water breaks when the amniotic sac in the uterus breaks open, either fully or partially.
The amniotic sac is the membrane that surrounds and protects your baby in the womb. When the sac ruptures, amniotic fluid leaks through the cervix and vagina. This is why your water breaking is called a rupture of membranes (ROM) in the medical world.
The sac can naturally rupture as your baby’s head moves down in the birth canal during labor. Or an outside force can rupture it, such as an accident or with a special instrument the doctor uses.
It can also rupture as a result of pregnancy complications, like an infection or polyhydramnios (when you have too much amniotic fluid).
In some situations, your water can also break for no real known reason, or it can break too early in your pregnancy.