The causes of premature rupture of membranes, or premature rupture of membranes, occur before labor when the membranes break. Normally, the membranes should rupture during labor when the cervix is fully dilated. Any rupture before this is called premature rupture of membranes. The main causes of premature rupture of membranes are maternal infections or cephalopelvic disproportion. Infections can cause the membranes to become fragile and thin, and movements afterwards may lead to premature rupture. Another scenario is cephalopelvic disproportion, where the fetus is relatively large and the pelvis is small, leading to changes in amniotic fluid pressure, which can also result in premature rupture of membranes.