Amniotic fluid

Amniotic fluid is the liquid that surrounds and protects a baby inside the womb during pregnancy. It cushions the baby, helps it move and develop, and keeps the temperature stable. When people talk about someone's "waters breaking," they mean the sac holding this fluid has ruptured.

• Amniotic fluid surrounds the baby in the womb from early pregnancy.
• It cushions the baby, helps with lung and muscle development, and keeps temperature steady.
• It's held inside a membrane called the amniotic sac.
• "Waters breaking" means the sac has ruptured — this usually happens during labour.

What it does

The amniotic fluid starts forming within the first couple of weeks of pregnancy. The baby floats in it inside a thin membrane called the amniotic sac. The fluid does a lot of important jobs: it acts as a shock absorber to protect the baby from bumps, gives the baby room to move (which helps muscles and bones develop), helps the lungs develop as the baby "breathes" it in and out, and keeps everything at a stable temperature.

As pregnancy progresses, the amount of fluid changes. It reaches its peak at around 36 weeks and then gradually decreases towards the end of pregnancy. Too much or too little fluid can sometimes be a sign that something needs medical attention, but most of the time levels are perfectly normal.

Waters breaking

"Waters breaking" is when the amniotic sac tears and the fluid starts to leak out. In films, this always happens dramatically in public — in real life, it's usually a slow trickle rather than a sudden gush. For most people, it happens during labour, but sometimes it happens before contractions start.

If someone's waters break before 37 weeks of pregnancy, that's called preterm prelabour rupture of membranes, and it needs medical attention straight away.

Things people ask about amniotic fluid

What colour is it?

Usually clear or slightly yellowish, sometimes with a faint pink tinge. If it's green or brown, that could mean the baby has passed meconium (its first poo) and medical attention is needed quickly.

Can the baby drown in it?

No. The baby doesn't breathe air in the womb — it gets oxygen through the umbilical cord. The fluid in the lungs actually helps them develop.

What does it smell like?

It's usually fairly odourless or has a very mild, slightly sweet smell. If it smells unpleasant, that could be a sign of infection.

Amniotic fluid is the liquid that surrounds a baby inside the womb while it is growing during pregnancy. The baby floats in this liquid inside a thin bag called the amniotic sac.

The fluid has lots of important jobs. It acts like a cushion to protect the baby from bumps. It gives the baby room to move around, which helps its muscles and bones grow. It also helps the baby's lungs develop and keeps everything at the right temperature.

The amount of fluid changes during pregnancy. It reaches its highest level at around 36 weeks and then slowly goes down towards the end.

When people talk about someone's "waters breaking," they mean this bag of fluid has burst. In films, this always happens in a big rush, but in real life it is usually more of a slow trickle. For most people, this happens during labour, but sometimes it happens earlier.

The fluid is usually clear or slightly yellowish. If it is green or brown, that means the baby needs medical help quickly. The baby cannot drown in this fluid because it does not breathe air inside the womb. It gets its oxygen through a cord attached to its belly.