Having too much amniotic fluid (Polyhydramnios) in Pregnancy

Image: Model of a baby in the womb, the space around the baby is where the amniotic fluid can be found.

What is polyhydramnios?

Polyhydramnios means having too much amniotic fluid, which is the water around your baby, during pregnancy. Amniotic fluid is important because it protects your baby and helps them grow and move. Doctors diagnose polyhydramnios using an ultrasound scan. Polyhydramnios is diagnosed when:

• Amniotic FIuid Index (AFI) is 25 cm or higher, or
• Deepest Vertical Pocket (DVP)  is 8 cm or higher

It can be mild, moderate, or severe, depending on how much extra fluid there is. Most women who have polyhydramnios have the mild form, which often causes no symptoms.

Why is it important?

Having extra fluid can sometimes make pregnancymore complicated.

Risks for the baby:

• A slightly higher chance of birth complications, especially if
  the extra fluid is caused by another condition
• Being born early also known as a preterm birth 
• Growing larger than an average birth weight, over 4 kg

Risks for the mother:

• Going into labour early
• If your baby is not head down such as bottom first, known as breech, or lying sideways, known as transverse
• Increased chance of needing a caesarean birth
• Higher risk of heavy bleeding after birth   

It is important to remember that many women with polyhydramnios have healthy pregnancies and babies. Careful monitoring helps reduce risk.

What causes polyhydramnios?

In around half of  pregnancies where polyhydramnios is
identified, no clear cause is found.  This is known as idiopathic polyhydramnios. 

Sometimes it may be linked to:

Mother’s health: developing diabetes as a result of pregnancy known as  gestational diabetes , certain infections, or rare medication side effects

Baby’s health: problems with swallowing or digestion, genetic conditions, or growth concern

Placenta: rare placental tumours

How will it be identified and monitored? 

A midwife will offer you an abdominal assessment at your routine antenatal appointments and at any attendance you may have through the Maternity Assessment Centre or Antenatal Day Unit. If polyhydramnios is suspected due to your bump measuring larger than expected and it is difficult to feel your baby’s position, you may be offered an ultrasound scan. 

If you are already having routine ultrasound scans in pregnancy to monitor your baby’s growth, the amniotic fluid volume is routinely measured during these scans.  

If polyhydramnios is confirmed, your care may include:

• Regular scans every 3–4 weeks to check fluid, baby’s growth, and blood flow
• Blood tests to check for diabetes and infections if needed
• Referral to a specialist at the fetal medicine unit if there are concerns about your baby

What are the symptoms?

Many women have no symptoms. However, if you get symptoms they may include:

• Feeling breathless
• Abdominal discomfort or tightness
• Swollen ankles or your tummy feeling very full

If symptoms are severe, your care team will discuss additional treatments, which may include drainage of some fluid at a specialist unit. This is not commonly needed.

Birth and labour

If you have polyhydramnios:

• You will have your own birth plan, in line with your wishes.
  We may recommend you give birth in a consultant-led maternity unit, where extra medical help is available.
• Before breaking your waters, an ultrasound may be done to check the baby’s position.
• Care will be taken to reduce risks such as the cord slipping down when your waters break, this is known as a cord prolapse.
• The team will be prepared for heavier bleeding after your baby is born and you will be given medication to help your womb contract.

Most women can have a vaginal birth, but occasionally a caesarean section may be recommended.

After birth

• Your baby will be checked carefully by the neonatal team, usually if the polyhydramnios was moderate or severe.
• If you were diagnosed with diabetes during pregnancy, you may need a follow-up blood sugar test.
• The placenta may be sent for specialist examination.

When to seek help urgently

Call your maternity unit straight away if you have:

Key points to remember

• Polyhydramnios means having too much amniotic fluid
• Most cases are mild and do not cause serious problems 
• Careful monitoring helps keep you and your baby safe 
• Your maternity team will make an individual plan for your pregnancy and birth 

This leaflet is based on guidance from the Royal College of Obstetricians and Gynaecologists (RCOG) and local hospital protocols at Bradford Teaching Hospitals.