Amniotic fluid: Amniotic fluid function and volume disorders

Amniotic fluid is a clear liquid that appears during the first 12 days after conception. Amniotic fluid surrounds the baby in the amniotic membrane and has several functions that are necessary for the normal development and growth of the fetus. However, if the amount of amniotic fluid inside the uterus is too little or too much, complications can occur in both mother and baby.

This article will talk about the functions of amniotic fluid, and share some disorders of amniotic fluid volume and its causes.


1. Some brief information about amniotic fluid

When the baby is in the womb, the baby is in the amniotic sac. The amniotic sac is made up of two membranes, the amniotic sac and the chorion. The baby in the womb develops inside this sac and is surrounded by amniotic fluid.

Amniotic fluid: Amniotic fluid function and volume disorders

A baby in the womb develops inside the amniotic sac and is surrounded by amniotic fluid

Initially, amniotic fluid is water from the mother's body. However, by about 20 weeks of pregnancy, the amniotic fluid is completely replaced by the baby's urine . This is because the baby in the womb swallows the amniotic fluid and urinates out.

Amniotic fluid also contains important nutrients, hormones, and antibodies. Besides, thanks to the support of water, it will help protect the baby from bumps and injuries.

If the amniotic fluid is too little or too much, it affects more or less the baby and mother.

When the amniotic fluid is green or brown, the baby has passed meconium before birth. Meconium refers to the first amount of stool a baby passes after birth.

When the amniotic fluid contains meconium, there will be some effects on the baby. This condition can cause a breathing problem known as meconium aspiration syndrome when the meconium enters the baby's lungs. In some cases, the baby will need to be treated after birth.

2. What is the function of amniotic fluid?

Amniotic fluid is responsible for:

  • Fetal protection:  Fluid cushions the baby from outside pressure. It acts as a cushion to help the baby limit shocks from the outside.
  • Temperature control:  Liquid insulates baby, keeps warm and maintains regular temperature.
  • Infection control:  Because the amniotic fluid contains antibodies.
  • Lung and digestive system development: By breathing and swallowing amniotic fluid, babies practice using these systems as they grow.
  • Muscle and bone development: As the baby floats inside the amniotic sac, it is free to move around. This gives your baby a chance to build muscles and bones to develop properly.
  • Lubrication: Amniotic fluid prevents body parts like fingers and toes from growing together. Therefore, when the amniotic fluid is too little, this development will not be complete and some organs or limbs may be attached.
  • Umbilical cord support:  The fluid in the amniotic sac prevents the umbilical cord from being compressed. The umbilical cord is responsible for transporting nutrients and oxygen from the placenta to the fetus.

Amniotic fluid: Amniotic fluid function and volume disorders

It plays a big role in the development of the fetus

Normally, amniotic fluid levels are at their highest around week 36 of pregnancy , usually around 1 liter. This amount of amniotic fluid may decrease near birth.

When the water breaks, amniotic fluid begins to flow out through the cervix, vagina, and out.

Water breaks usually occur towards the end of the first stage of labor, that is, after the cervix is fully dilated. According to Parent's Today , only about 15% of women have their membranes ruptured before labor begins – regular, painful uterine contractions. When you see that your water breaks, you need to prepare to go to the nearest reputable obstetrics and gynecology center for monitoring. Because broken water is a sign that labor is imminent.

3. What amniotic fluid disorders can occur?

Certain conditions in the mother and fetus can cause the amount of amniotic fluid to be less or more than normal. There are two commonly used terms:

  • Oliguria is when there is too little amniotic fluid.
  • Polyhydramnios is when there is too much amniotic fluid.

3.1. What is oligohydramnios?

When the level of amniotic fluid is too low, it is called oligohydramnios. This condition occurs in about 4% of all pregnancies.

It is called oligohydramnios when the amniotic fluid index (AFI) is ≤ 5 cm or the maximum amniotic cavity is ≤ 2 cm. Normally, the amniotic fluid index will be in the range of 5-25 cm. These stains are measured during fetal ultrasound.

Amniotic fluid: Amniotic fluid function and volume disorders

oligohydramnios when amniotic fluid index (AFI) 5 cm or maximal amniotic cavity 2 cm

However, before being assessed as oligohydramnios, the doctor will examine and examine the mother's vagina to rule out whether this little amniotic fluid is due to amniotic fluid leaking outside.

Mothers with the following health problems are among the risk factors for oligohydramnios:

  • Thai growth retardation.
  •  Chronic hypertension.
  • Preeclampsia .
  • Pre-existing diabetes or gestational diabetes.
  • Systemic lupus.
  • Multiple pregnancy, eg twins or triplets.
  • Congenital anomalies, such as renal parenchymal abnormalities.
  • Pregnancy past due date.
  • No obvious cause can be found, also known as idiopathic.

oligohydramnios can occur at any stage of pregnancy. However, it mostly occurs in the first 6 months of pregnancy. During this time, oligohydramnios will often be associated with a fetus with birth defects. The rate of pregnancy loss or postpartum loss also occurs higher than normal.

If oligohydramnios is in the last trimester, risks may include:

  • Fetal growth retardation in utero.
  • Uterine contractions disorder.
  • If necessary, your doctor may recommend a cesarean section.

When oligohydramnios is detected, the later stages of pregnancy will need to be closely monitored to ensure the normal development of the baby.

Doctors may additionally recommend:

  • Non-stress test:  This type of test checks the baby's heart rate when the baby is at rest and when there is fetal movement.
  • Routine pregnancy ultrasound: An ultrasound can detect the baby's movements, muscle tone, breathing rate, and amniotic fluid volume.
  • Check the fetus machine: Fetal movement is an indicator of the health status of the fetus. When the number of fetal movements decreases, it is a warning sign of poor health of the fetus. Mechanical pregnancy is a method to help mothers monitor the baby in the womb.
  • Color Doppler ultrasound: Helps to visualize the renal artery. Study of fetal blood flow: Helps to confirm the diagnosis of intrauterine growth retardation and assess the health of the fetus.

In some cases, doctors may decide early labor or a cesarean section is needed to protect the mother and baby.

Methods to increase the amount of amniotic fluid such as amniotic fluid infusion, advise the mother to drink a lot of water to support the development of the baby's lungs when oligohydramnios in the second trimester of pregnancy.

3.2. What is polyhydramnios?

When there is too much amniotic fluid, the condition is called polyhydramnios. According to the American College of Obstetricians and Gynecologists, polyhydramnios occurs in about 1% of pregnancies.

The condition is called polyhydramnios when the amniotic fluid index (AFI) is ≥ 25 cm or the maximum amniotic cavity (MVP) is ≥ 8 cm.

Amniotic fluid: Amniotic fluid function and volume disorders

Polyhydramnios when amniotic fluid index (AFI) 25 cm or maximal amniotic cavity (MVP) 8 cm

Fetal abnormalities that can lead to polyhydramnios include:

  • Blood transfusion when having twins, especially identical twins.
  • Birth defects such as esophageal stricture, central nervous system abnormalities (cerebrovascular).
  • Abnormalities causing blood circulation overload such as: Tumor in the placenta, hemangioma in the fetus...
  • No obvious cause (idiopathic): accounts for 60% of polyhydramnios.

Maternal conditions that can lead to polyhydramnios include:

  • Diseases such as hypertension, diabetes, cardiovascular disease, severe anemia.
  • Having an infection such as syphilis , Toxoplasma infection, rubella…
  • Blood type incompatibility between mother and child.

Maternal symptoms may include: Abdominal pain and difficulty breathing due to an overstretched uterus.

Complications that can occur with polyhydramnios include:

  • Premature birth .
  • Early rupture of membranes.
  • Baby placenta.
  • Stillbirth (fetal loss in the womb).
  • Postpartum haemorrhage (postpartum haemorrhage).
  • Fetal malformations.
  • Wrap the umbilical cord.

When polyhydramnios is present, you will be asked to check your blood sugar and have regular ultrasounds to monitor the level of amniotic fluid in your uterus. Mild cases of polyhydramnios usually do not require further treatment and monitoring.

In the case of breathing difficulties for the mother, it is necessary to reduce the amount of amniotic fluid by amniocentesis.

3.3. Leakage of amniotic fluid

In some cases, the amniotic fluid can leak out without causing the water to rupture massively. According to the American College of Obstetricians and Gynecologists, 1 in 10 women with a full-term pregnancy will have massive rupture of membranes. However, most women will feel a leak or small amniotic fluid coming out.

In some cases, urine leakage is mistaken for amniotic fluid leakage. Leakage of urine (urinary leakage) is a normal symptom of pregnancy, especially near the time of delivery. Because at this time, the uterus is large and the baby's head falls below the pelvis, pressing on the bladder and causing urine to leak out.

>> Don't be alarmed by frequent urination during pregnancy. Please supplement your knowledge through the following article: Frequent urination during pregnancy: Some notes for mothers .

Amniotic fluid: Amniotic fluid function and volume disorders

Amniotic fluid leaking out

If the discharge is colorless or slightly cloudy, odorless, or has a slight fishy odor, it could be amniotic fluid. At this time, you need to go to the Obstetrics and Gynecology Center as soon as possible. Because the process of going into labor will start happening early.

If the amniotic fluid has an unusual color like green or brownish brown or has a foul odor, it could be due to the presence of meconium in the amniotic fluid or an infection of the amniotic fluid. At this time, the doctor will examine, examine and give more advice to the mother.

3.4. Premature rupture of membranes/Premature rupture of membranes

If the water breaks during labor, before the cervix is ​​fully dilated, it is called premature rupture of membranes.

Premature rupture of membranes is when the water breaks before labor occurs. If labor goes into labor 1 hour after the water breaks - uterine contractions are regular and painful - it's still not present, it's called preterm rupture of membranes.

Premature rupture of membranes occurs in about 2% of all pregnancies. The membranes can rupture very early, around the 5th month of pregnancy. However, it is more common for the membranes to rupture in the last 1-2 months of pregnancy.

Depending on the time of rupture of membranes at full-term or preterm pregnancy, what week the fetus is in, how long the water has broken, whether there are signs of amniotic infection or not, there will be different treatment for the mother.

As such, amniotic fluid has many roles in pregnancy. The volume of amniotic fluid alone provides some useful information in pregnancy care. Therefore, good pregnancy management by regular antenatal checkups helps the doctor and the mother to identify abnormal amniotic fluid volume if present. This helps to assess the cause and its effect on the pregnancy. From there, you can create a management plan to have a healthy pregnancy.