Amniotic fluid

Amniotic fluid is the fluid that surrounds your baby in your uterus (womb). It’s very important for your baby’s development.

How does amniotic fluid keep your baby healthy?

During pregnancy, your uterus is filled with amniotic fluid. Here’s what the fluid does:

  • Cushions and protects your baby
  • Keeps a steady temperature around your baby
  • Helps your baby’s lungs grow and develop because your baby breathes in the fluid
  • Helps your baby’s digestive system develop because your baby swallows the fluid
  • Helps your baby’s muscles and bones develop because your baby can move around in the fluid
  • Keeps the umbilical cord (the cord that carries food and oxygen from the placenta to your baby) from being squeezed

The amniotic sac (bag) inside the uterus holds your growing baby. It is filled with amniotic fluid. This sac forms about 12 days after getting pregnant.

In the early weeks of pregnancy, the amniotic fluid is mostly water that comes from your body. After about 20 weeks of pregnancy, your baby’s urine makes up most of the fluid. Amniotic fluid also contains nutrients, hormones (chemicals made by the body) and antibodies (cells in the body that fight off infection).

How much amniotic fluid should there be?

The amount of amniotic fluid increases until about 36 weeks of pregnancy. At that time, it makes up about 1 quart. After that, the amount of amniotic fluid usually begins to decrease.

Sometimes you can have too little or too much amniotic fluid. Too little fluid is called oligohydramnios. Too much fluid is called polyhydramnios. Either one can cause problems for a pregnant woman and her baby. Even with these conditions, though, most babies are born healthy.

Does the color of amniotic fluid mean anything?

Normal amniotic fluid is clear or tinted yellow. Fluid that looks green or brown usually means that the baby has passed his first bowel movement (meconium) while in the womb. (Usually, the baby has his first bowel movement after birth.)

If the baby passes meconium in the womb, it can get into his lungs through the amniotic fluid. This can cause serious breathing problems, called meconium aspiration syndrome, especially if the fluid is thick.

Some babies with meconium in the amniotic fluid may need treatment right away after birth to prevent breathing problems. Babies who appear healthy at birth may not need treatment, even if the amniotic fluid has meconium.

Last reviewed: June, 2013