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Amniotic Fluid Issues - Too Little, Too Much

amniotic fluidAmniotic fluid is usually derived from baby's urine and it is inside the protective sac that your baby lives in inside your uterus. Amniotic fluid serves many purposes, all for the betterment and protection of your unborn child. Naturally, because of its importance, several issues may arise if the amount of amniotic fluid is not correct.

Oligohydramnios, for example, means that there is not enough amniotic fluid inside the uterus surrounding the fetus. Not having enough amniotic fluid can lead to several complications.

Amniotic fluid serves the following purposes:

  • Provides a cushion to protect the child from trauma (should you fall).
  • Keeps the umbilical cord from becoming compressed and reducing the oxygen supply to your baby.
  • Keeps the child moving so that bones develop correctly.
  • Prevents infection, and helps to keep a regulated temperature in the womb.

The amount of amniotic fluid is measured either by checking the largest pocket of fluid by ultrasound or by measuring the largest amniotic fluid pocket in each of four quadrants and then adding those up. This is called the AFI or Amniotic Fluid Index.

Finding an amniotic fluid pocket that's at least 2 cm in vertical diameter is usually considered adequate. Alternatively, any AFI more than 25 cm gives you too much amniotic fluid, and any AFI less than 5 cm during the third trimester is too low.

Because the AFI has too many "false positive" results (too many people diagnosed with too low fluid when in fact the outcome was OK), the single pocket amniotic fluid evaluation has recently been found more reliable than the AFI. Any single pocket that's over 2 cm is considered adequate.

Too Much Amniotic Fluid- Polyhydramnios
If you have too much amniotic fluid, your uterus is likely growing faster than it should.  This generally occurs within roughly one percent of all pregnancies. There are several potential causes for hydramnios or polyhydramnios, the formal name for the condition of having too much amniotic fluid. These causes could be:

  • Maternal Diabetes: In ten percent of diabetic mothers, this condition presents itself because of difficulty managing the diabetes.
  • Carrying Multiples: One child can take too much blood from the other which increases the risk for this condition.
  • Fetal Abnormalities: In rare cases, the baby stops swallowing the fluid and no longer passes it through his or her kidneys.
  • Fetal Anemia: Even rarer, the baby could have an infection or Rh compatibility issue that can be treated with blood transfusions.

Too Little Amniotic Fluid - Oligohydramnios
If you have too little amniotic fluid, a condition known as oligohydramnios, there could be several different causes as well. Your healthcare professional will likely suspect this if you are leaking fluids from an early stage (or too soon) in your pregnancy, or if you have had a previous pregnancy where you experienced preeclampsia, restricted growth of the child, or diabetes. An estimate 8% of pregnancies have this condition at some point during the third trimester of pregnancy, and 12% of women who go to two weeks past their due date have this condition. Causes for this condition could be:

  • Ruptured/Leaky Membranes: May heal itself, but increases risk of infection to the unborn.
  • Placental issues: Causes reduction in nourishment to the child and therefore stops the recycling process the child creates when he or she drinks and processes the fluid through the kidneys.
  • Certain medical conditions: diabetes, preeclampsia, high blood pressure, etc.
  • Carrying multiples
  • Fetal abnormalities: The baby’s kidneys may not be functioning, or there could be a congenital heart defect.

What happens?
In either case, your doctor will perform an ultrasound to confirm the presence of an excess or lack of amniotic fluid. The sonographer will measure the fluid in four large pockets in order to find out where you rate on the amniotic fluid index (AFI). Anything more than 25 cm gives you too much amniotic fluid, and anything less than 5 cm during the third trimester is too low. 

If you have too much fluid, you will likely have an amniocentesis to test for abnormalities and genetic issues. Testing for gestational diabetes will likely be done, and you will undergo regular ultrasounds and stress tests to monitor the condition of your baby. If you have too little fluid, you will be closely monitored until delivery.

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