What is amniotic fluid?

Amniotic fluid is a watery liquid that surrounds and protects your baby in the uterus during pregnancy. It is contained in the amniotic sac.

How is amniotic fluid produced?

During the early weeks of pregnancy, amniotic fluid is produced by your body. As your baby grows and develops, they will start to produce most of the amniotic fluid through their urine and fluid from their lungs.

Why is amniotic fluid important during pregnancy?

Amniotic fluid is important during pregnancy for your baby's growth and development. It helps:

• your baby move around in your uterus
• your baby's lungs, digestive system and muscles develop
• maintain a normal temperature around your baby
• cushion and protect your baby from pressure or outside injury

How is amniotic fluid assessed?

Amniotic fluid can be assessed and measured using ultrasound. The ultrasound probe will be placed on your abdomen (tummy). Your healthcare professional will look for pockets of amniotic fluid around your baby and check how much fluid there is. The amount of fluid is usually described in centimetres and is called the Amniotic Fluid Index (AFI).

What do the results of this test mean?

The amount of amniotic fluid around your baby provides some information about your baby's wellbeing. Too much or too little fluid can be associated with pregnancy complications. It can sometimes be a sign that there's a problem.

For this reason, the amount of amniotic fluid you have is often measured during your routine pregnancy ultrasounds.

Read about waters breaking early (preterm prelabour rupture of membranes).

Read about waters breaking (prelabour rupture of membranes or spontaneous rupture of membranes).

How much fluid is normal?

Healthy amounts of amniotic fluid can range widely, from 500 to 2000 millilitres (mL). The amount of amniotic fluid you have increases throughout pregnancy until you reach 34 weeks.

The amount of amniotic fluid you have also varies from person to person and in each pregnancy.

If you are unsure about your amniotic fluid index, speak with your midwife or doctor to understand what your results mean for you and your baby.

What if the amount of fluid is not normal?

In some pregnancies, the amount of amniotic fluid may be higher or lower than expected. This can be due to a pregnancy complication, and may sometimes be a sign that there's a problem.

• Oligohydramnios is the medical term used to describe having low or not enough amniotic fluid.
• Anhydramnios is the medical term used to describe when there is no amniotic fluid seen on an ultrasound.
• Polyhydramnios is the medical term used to describe having too much or more fluid than expected.

What high or low fluid levels mean for you and your baby depends on the cause (if known), how severe it is and how far along you are in your pregnancy.

If your amniotic fluid index is too high or too low, your doctor or midwife will explain what this means for you. They can answer any questions you have, including the likely causes and how to manage this.

Read more about pregnancy checkups, screenings and scans.

Resources and support

Queensland Health has an informative fact sheet explaining what to do if your waters break early.

The Department of Health, Disability and Ageing has a guide outlining your pregnancy timeline.

Languages other than English

Miracle Babies Foundation has translated their webpage about Preterm Premature Rupture of Membranes (PPROM) into many community languages.

Information for Aboriginal and/or Torres Strait Islander peoples

You can find out more about Aboriginal and/or Torres Strait Islander peoples'pregnancy health at Stronger Bubba Born or watch the 'How to Have a Safer Pregnancy' video.