Amniotic Fluid
Clear Liquid Surrounding The Growing Fetus

Pregnancy Guidelines

Baby floating in Amniotic Fluid
Fetus floating in amniotic fluid contained in the amniotic sac.

Amniotic Fluid


What Is Amniotic Fluid?
What Is The Purpose Of It?
Why Do Doctors Test Amniotic Fluid?
Too Much Or Too Little Fluid?
Can I Test For Amniotic Fluid Leakages At Home?

What Is Amniotic Fluid?

It is a clear, slightly yellowish fluid that surrounds the fetus (unborn baby) during pregnancy. It is contained within the amniotic sac in the mother's womb. The fluid may also contain small solid particles derived from the baby's skin and lanugos hairs (light hairs on the baby's skin). It can also be stained a green or brown colour if any meconium (baby's faeces) has been passed into it. While in the womb, the baby floats around in the amniotic fluid and swallows or inhales the fluid and then releases it again. It is not however regarded as a source of nutrition because it doesn’t contain many nutrients. Instead, the mother supplies her fetus nutrients via the placenta and umbilical cord. The volume of the amniotic fluid at term is about 800 ml (although it can range from 400 to 1500 ml in normal cases). At 10 weeks the average volume is 30 ml, at 20 weeks 300 ml and at 30 weeks 600 ml. The rate of increase is about 30 ml per week, but the rate falls off as the delivery date approaches.

What Is The Purpose Of Amniotic Fluid?

Protects the baby: The liquor guards the fetus against injury from outside, it equalizes the pressure exerted by uterine contractions and allows, at least in the early months, plenty of room for fetal movement and growth.
Provides a regular temperature: Since the temperature of the fluid is maintained by the mother, the fetus is not subjected to loss of heat. This means it does not need to spend valuable energy trying to heat itself, it can there divert all energy entirely to growth. This reserve of energy boosts development of the lungs, digestive system and muscles.
Lung development: The fetus inhales and exhales the fluid which helps prepare the lungs for its first breath after delivery.
Helps with childbirth: During labor the fluid forms a ‘fluid wedge’ which helps to dilate the cervical canal for childbirth. Additionally, when the membranes rupture the fluid flushes the vaginal canal acting like a natural antiseptic and antibacterial wash.

Why Do Doctors Test Amniotic Fluid?

Samples of the fluid can be obtained during pregnancy for various diagnostic purposes by abdominal amniocentesis (sometimes called the amniotic fluid test). This invasive procedure (picture) involves injecting a long hollow needle through the stomach, guided by ultrasound, to extract a sample of the amniotic fluid. This sample can provide information about the health, gender and development of the fetus. A chromosomal study can be performed on the sample to test for genetic disorders like Down syndrome. See also genetic testing during pregnancy.

Too Much Or Too Little Fluid?

Polyhydramnios: This is where there is too much amniotic fluid because the baby is not swallowing it in normal amounts. It can occur with multiple pregnancy (twins or triplets), congenital anomalies (where the baby has a problem such as a gastrointestinal disorder or lung problem) or gestational diabetes. Sometimes there is no specific cause.
Oligohydramnios: This condition is characterized by an abnormally small amount of amniotic fluid. Most cases are the result of a puncture in the amniotic sac, causing the fluid to leak. Less common causes include intrauterine growth restriction (IUGR) and birth defects. Most women with oligohydramnios fortunately go on to have completely normal pregnancies, although there is a slight risk of umbilical cord restriction if there is too little fluid for the baby to float around in.

Can I Test For Amniotic Fluid Leakages At Home?

amniosense panty liner

Yes, you can. You can buy a special panty liner that is designed to be used after week 36 of pregnancy which helps to identify the nature of any leakage (it may turn out just to be urine). Simply attach the liner to your underwear and after you feel a fluid leak, remove the indicator strip which is inserted in the liner. The strip will turn a specified colour if it detects amniotic fluid or a vaginal yeast infection. If you have a positive result you should call your doctor straight away. Early detection of amniotic leakages can:

• Prevent pregnancy complications or premature births.
• Identify a possible rupture of the membrane, this is a potential complication of amniocentesis.
• Confirms that your waters have broke, so you can start making your way to hospital in time for delivery.

In the UK, the panty liners are sold under the brand name AmnioSense and in the U.S. by AL-Sense.

  Related Articles on Pregnancy

For more information, see the following:

The Female Body

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