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Date issued: August 2021

Review date: August 2023

Ref: A-474

PDF:  Mild Polyhydramnios final August 2021.pdf [pdf] 87KB

What is polyhydramnios?

Polyhydramnios is a condition where the amniotic fluid surrounding your baby is increased during pregnancy.

What is amniotic fluid?

Amniotic fluid is predominately made up of fluid from fetal urine production after the first 12 weeks of gestation. The fluid provides cushioning to help protect your baby and allows your baby to move which aids muscle and bone development. The lungs and digestive system develop as the fluid is swallowed by your baby, absorbed, and then passed out as urine. Polyhydramnios is diagnosed when there is too much fluid being produced.

What causes polyhydramnios?

The cause of polyhydramnios is not known for around 50% of cases. Polyhydramnios can be caused by a reduced fetal swallowing and absorption or an increase in fetal urine production. Increased fetal urine production can also be linked with the mother developing diabetes during pregnancy also known as gestational diabetes. Polyhydramnios can be identified during your ultrasound scan and can be classed as mild, moderate or severe depending on the amount of fluid.

What happens next?

Amniotic Fluid Index (AFI) is the term used to estimate the amount of amniotic fluid around your baby. If the AFI measurement is between 25-30cms a Glucose tolerance test (GTT) or capillary blood glucose monitoring will be arranged to check for gestational diabetes unless already performed within four weeks. The sonographer will also arrange a follow up scan in four weeks to determine the AFI levels and fetal growth. If the AFI measurement is below 30cms (mild polyhydramnios) there is no need for any future follow up. If the measurement is above 30cms you will then be referred to the Fetal Medicine consultants who will perform another ultrasound.

What complications are associated with Polyhydramnios?

Very rarely there are complications that can happen when there is more fluid around your baby than we would usually expect.  These can include: 

• Premature rupture of membranes (PROM)

• Placental abruption

• Umbilical cord prolapse

• Premature birth

• Unstable lie

These complications are very rare especially with mild polyhydramnios.  The risks are higher the more fluid is present, especially if the amniotic fluid index (AFI) is over 30cms. Even in these cases the risks are low of the complications listed above.

If your Polyhydramnios is mild, and your glucose testing is normal, you will be able to continue your pregnancy with the expectation that you will go on to have a normal remainder of the pregnancy and delivery.

If you have any questions these can be discussed with your midwife. If you have any concerns you can contact Triage on 01752 430200. Thank you for reading this information leaflet and we welcome any feedback.