Increased volume of amniotic fluid in utero of more than 1500ml. This occurs in around 1% of pregnancies, and within that 1%, around 70% of cases are mild and around 10% are severe. For the majority of polyhydramnios cases, the cause is unknown (some research suggests around 40% of cases have a known cause although this figure varies). Some causes can include multiple pregnancies, gestational diabetes, and infection. Most cases are managed using expectant management, involving an increased number of appointments with your Midwife or Obstetrician where your bump will be measured, and an increased number of scans to monitor the depth of the deepest pool of amniotic fluid in your womb.