The amniotic fluid is part of the baby’s life support system. It protects your baby and aids in
the development of muscles, limbs, lungs and the digestive system. Amniotic fluid is produced soon after the
amniotic sac forms, about 12 days after conception. It is first made up of water that is provided by the mother.
After about 20 weeks into the pregnancy, it is primarily made up of fetal urine. As the baby grows, he or she will
move and tumble in the womb with the help of the amniotic fluid. In the second trimester the baby will begin to
breathe and swallow the amniotic fluid. Amniotic fluid levels increase regularly until about 32-33 weeks gestation,
and then they level off. In some cases the amniotic fluid may measure too low or too high. Normal fluid levels may
vary, but are usually considered an AFI of 5-25 centimeters or a fluid level of about 800-1000 mL. If the
measurement of amniotic fluid is too low it is called oligohydramnios. If the measurement of amniotic fluid is too
high it is called polyhydramnios.
What is Polyhydramnios?
Polyhydramnios is the condition of having too much amniotic fluid. Doctors can measure the
amount of fluid through a few different methods, most commonly through amniotic fluid index (AFI) evaluation or
deep pocket measurements. If an AFI shows a fluid level of more than 25 centimeters (or above the 95th percentile),
a single deep pocket measurement of <8, or a fluid level of 2000mL or more, then a diagnosis of polyhydramnios
would be made. About 1-2% of pregnant women have too much amniotic fluid. Most of these cases are mild, with only
slightly elevated levels.
What causes levels of amniotic fluid to be elevated?
Congenital defects – The higher the fluid level, the increased chance of a
congenital defect. These birth defects hinder swallowing, which can prohibit ingestion of the amniotic fluid,
resulting in build up of fluid. Other birth defects could also include intestinal tract blockage or neurological
Rh Factor – As screening for the Rh factor has increased, this is no longer a
common cause of elevated fluid levels.
Maternal Diabetes – Experts have found some correlation between diabetes and
too much amniotic fluid.
Twin-to-twin transfusion syndrome – This is a complication that can affect
identical twin pregnancies. This syndrome is when one baby gets too much blood flow and the other too little due to
connections between blood vessels in their shared placenta.
Unknown Reasons – According to the Center for Maternal Fetal Medicine, about
65% of cases of polyhydramnios are due to unknown causes.
What are the risks of having too much amniotic fluid?
Most cases of polyhydramnios are mild and result in few, if any, complications. Those with
higher levels of fluid could experience one or more of the following risks:
Premature rupture of the membranes (PROM)
Preterm labor and delivery (approximately 26%)
Growth restriction (IUGR) resulting in skeletal malformations
Stillbirth occurs in about 4 in 1000 pregnancies that suffer from polyhydramnios vs. about 2 in1000
pregnancies with normal fluid levels.
What are the treatments for elevated amniotic fluid
Many cases of polyhydramnios are easily treated and do not result in complications if the
pregnancy is monitored closely. Monitoring would include frequent sonograms measuring growth, biophysical profile
and fetal assessment. Other treatments could include:
Medication that can reduce fluid production and are as much as 90% effective. This treatment is not
used after 32 weeks gestation because of possible complications.
Amnioreduction is a procedure that can be used to drain excess fluids. This is done through
amniocentesis, which may carry certain risks. There is, however, the chance that fluid could build back
up even after draining.
Delivery of the baby