• Baby on the Way

Amniotic Fluid: Too Much Or Too Little?

Amniotic fluid is an essential part of your developing baby’s life support system in the uterus. This liquid protects and cushions your baby and plays a role in developing her lungs, muscles, and digestion. She swallows and breathes in amniotic fluid and recycles it through urine output.

Amniotic fluid is measured by an ultrasound assessment.  This can be problematic, as ultrasound uses a one or two dimensional measurement to estimate a volume, which is three dimensions.  Ultrasound is the best available method, but it is often inaccurate and under or over estimates the volume of fluid. 

Most pregnant women have about half a quart to a quart of amniotic fluid. But about 8 percent have less than that, and about 4 percent of them are diagnosed with oligohydramnios, or low amniotic fluid levels. On the other hand, around 1 percent of pregnant women have polyhydramnios, or excessive amniotic fluid.

Having too little or too much amniotic fluid can cause pregnancy complications. If detected early, in the first half of pregnancy, these problems can be more severe.

Possible Complications

Having too little or too much amniotic fluid can cause pregnancy complications. If detected early, in the first half of pregnancy, these problems can be more severe:

• Complications from low amniotic fluid levels (oligohydramnios)

  Since the growth of lungs, limbs, and muscles depend on amniotic fluid, detection of oligohydramnios in the first half of pregnancy could mean that the baby’s lungs will not develop properly and the baby may not be able to breath when born.  Also the organs are compressed and there is an increased risk of miscarriage or stillbirth. If it’s detected in the second half of pregnancy, complications may include intrauterine growth restriction, preterm labor, and certain labor complications such as cord compression, meconium in fluid, and C-section.

• Complications from high amniotic fluid levels (polyhydramnios)

  Mild polyhydramnios, in most cases, does not cause complications. But in severe cases, problems may include premature birth, preterm labor, placental abruption (the placenta detaches from the uterus wall too early), excessive fetal growth, cord prolapse (the umbilical cord drops through the cervix ahead of the baby), postpartum hemorrhage, fetal malposition, or stillbirth.

Causes Of Amniotic Fluid Problems

Many times, the cause of amniotic fluid level problems is unknown. But low amniotic fluid can be caused by:

• Ruptured membranes: This is the most common cause of low amniotic fluid.
• Problems with the placenta: The placenta may not provide enough blood and fluid to the baby, so the baby cannot recycle the fluid.
• Birth defects: The baby’s kidneys may not be able to produce enough urine, which means lower fluid levels.
• Post-date pregnancy: Amniotic fluid may decrease after 41 weeks of pregnancy.
• Issues with the mother: Hypertension, dehydration, diabetes, preeclampsia, and chronic hypoxia (a condition in which cells and tissues in the body receive inadequate oxygen) can affect amniotic fluid levels.

Excess amniotic fluid may be caused by these issues:

• Birth defect: Sometimes polyhydramnios can be caused by a defect in the baby’s ability to swallow (since the baby swallows the amniotic fluid and eliminates it as urine).
• Twin-to-twin transfusion syndrome: Sometimes one identical twin can receive too much blood and the other, too little.
• Maternal diabetes: High blood glucose levels can lead to high amniotic fluid levels.
• Mismatched blood types: If the mother has the RH-negative blood type and her baby is RH-positive, one side effect can be polyhydramnios.
• An infection in the baby
• Problems with the baby’s heart rate

Treatment For Amniotic Fluid Level Problems

The treatment for amniotic fluid level problems depends on how far along you are in pregnancy and whether you have too much or too little.

If you have too much amniotic fluid, you will be monitored carefully. Mild polyhydramnios will probably not require treatment.

Severe polyhydramnios treatment will depend upon the underlying cause. One treatment method is regularly withdrawing fluid from the uterus using a large needle. This can pose risks, so your doctor will decide whether the risk of excess amniotic fluid outweighs the risk of the procedure.

If you have too little amniotic fluid, treatment will depend on your stage of pregnancy. If you are early in pregnancy, you and your baby’s activity will be monitored carefully. If you are full term or close to full term, your labor may be induced early.

Other treatments include infusion of fluids through a small catheter during labor to provide padding around the umbilical cord, amniocentesis to inject fluid before labor, and oral or IV rehydration of the mother.

Sources: American Pregnancy Association; March of Dimes; Stanford Children’s Health