Polyhydramnios (increased fluid around your baby)

Polyhydramnios is a condition where the water around your baby (also called amniotic fluid) is increased during pregnancy.

Your ultrasound scan has shown that the fluid level around your baby is increased. This information should help you to understand polyhydramnios and how this might affect your pregnancy care.

Amniotic fluid

Amniotic fluid is a protective liquid, made up mostly of fluid from fetal urine production after the first 12 weeks of gestation.

The fluid cushions your baby and allows your baby to move which helps muscle and bone development. The fluid is swallowed by your baby, absorbed, and then passed out again as urine, helping the lungs and digestive system to develop.

In some cases, there may be too much or too little fluid. When there is too much fluid, it is called polyhydramnios.

Causes of polyhydramnios

The cause of polyhydramnios in a singleton pregnancy (when you are pregnant with one baby) is not known for 4 in every 5 cases.

Polyhydramnios can be caused by a reduced fetal swallowing or an increase in fetal urination. Reduced fetal swallowing can be related to a bowel blockage.

An increased urine production can be linked sometimes with the mother developing diabetes during pregnancy (also called as gestational diabetes).

Polyhydramnios can be classed as mild, moderate or severe depending on the amount of amniotic fluid volume that is found during your ultrasound scan.

What happens next?

The sonographer (a health professional who specialises in ultrasound imaging) will measure the amount of amniotic fluid around your baby.

Amniotic fluid index (AFI) is the term used to estimate the amount of amniotic fluid around your baby. Sometimes the sonographer may measure this as a deepest vertical pool (DVP), which is the largest or deepest measurement of fluid around the baby.

If the AFI or DVP is above the normal levels, the sonographer will assess your baby’s stomach, kidneys and bladder to exclude any major problem. They will also check or sometimes as for baby’s movements.

You may also be offered blood tests for gestational diabetes.

If your glucose test result is normal, you will be followed up by your consultant. Your baby will be reviewed after birth by the neonatal team (to check the swallowing of the baby).

If your glucose test result is abnormal (you have a high level of glucose in your blood), we will organise further a test to assess if you have developed gestational diabetes.

The sonographer will also arrange an appointment to see your consultant within 7 to 10 days to review your scan and blood test results.

Severe polyhydramnios

If the level of the AFI is very high (severe polyhydramnios), a further detailed scan will be arranged for you in the fetal medicine unit. We might offer you other blood tests or investigations, in addition to the testing for gestational diabetes and consultant appointment.

Rarely, you may feel uncomfortable due to the amount of amniotic fluid. The fetal medicine specialists may discuss draining some of the fluid from your abdomen to alleviate your discomfort. Most women usually do not need this intervention.

Resource number: 4178/VER2
Last reviewed: August 2023
Next review: August 2026

A list of sources is available on request.

Contact us

If you have any questions or concerns, please contact the fetal medicine midwives.

Phone: 020 7188 2321 Monday to Friday, 9am to 5pm.

You can also call the maternity assessment unit (MAU) on 020 7188 1723 at any time.

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

Is this health information page useful?