17.3.3 Multiple pregnancy and excess amniotic fluid
If the uterus holds two or more babies, or there is excess accumulation of amniotic fluid (polyhydramnios), the fetal membranes become over-stretched and rupture. The membranes can rupture even if the amount of amniotic fluid is small, if there is another cause such as those described below.
‘Poly’ means excess, ‘hydra’ means water, and ‘amnios’ refers to the amniotic fluid. So ‘polyhydramnios’ means ‘too much amniotic fluid’.