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High-Risk Pregnancy: Oligohydramnios

Too much or too little amniotic fluid

Amniotic fluid is an important part of pregnancy and fetal development. This watery fluid is inside a casing called the amniotic membrane (or sac) and fluid surrounds the fetus throughout pregnancy. Normal amounts may vary, but, generally, women carry about 500 ml of amniotic fluid. Amniotic fluid helps protect and cushion the fetus and plays an important role in the development of many of the fetal organs including the lungs, kidneys, and gastrointestinal tract. Fluid is produced by the fetal lungs and kidneys. It is taken up with fetal swallowing and sent across the placenta to the mother's circulation. Amniotic fluid problems occur in about 7 percent of pregnancies.

Hydramnios (too much amniotic fluid) poses a greater threat to the mother, whereas Oligohydramnios (too little of amniotic fluid) poses greater danger to the life of the fetus that she is carrying.

The Amniotic Fluid Index

How is the level of amniotic fluid measured? Your health care provider uses ultrasound to measure the depth of the amniotic fluid in four different areas of your uterus and adds up the results. This is your amniotic fluid index. If the amniotic fluid depth is less than 5 centimeters (cm), you have oligohydramnios. If the depth measures greater than 25 cm, you have polyhydramnios.


Oligohydramnios is a condition in which there is too little amniotic fluid around the fetus. The condition is often the result of a tear or rupture in the amniotic membrane, causing it to leak amniotic fluid and thus lower the level of fluid still surrounding the baby It occurs in about 4 percent of all pregnancies.

What causes oligohydramnios?

There are several causes of oligohydramnios. Generally, it is caused by conditions that prevent or reduce amniotic fluid production. Factors that are associated with oligohydramnios include the following:

  • Premature rupture of membranes (before labor)

  • Intrauterine growth restriction (poor fetal growth)

  • Post-term pregnancy

  • Birth defects, especially kidney and urinary tract malformations. If his kidneys aren't developing properly (Potter's syndrome) or his urinary tract is blocked, your baby won't be able to produce enough urine to keep the level of amniotic fluid up.

  • Twin-to-twin transfusion syndrome - This happens when there's a problem with the placenta and one twin ends up with a disproportionate share of the blood supply. The "donor" twin suffers from low amniotic fluid, while the "recipient" twin usually ends up with too much. About two-thirds of twins with this syndrome don't survive the pregnancy.

  • Certain drugs may cause oligohydramnios, including ACE inhibitors, which are often used for management of high blood pressure, and prostaglandin inhibitors, such as indomethacin or even ibuprofen. You should avoid these drugs during pregnancy

Amniotic fluid is important in the development of fetal organs, especially the lungs. Too little fluid for long periods may cause abnormal or incomplete development of the lungs called pulmonary hypoplasia. Intrauterine growth restriction (poor fetal growth) is also associated with decreased amounts of amniotic fluid. Oligohydramnios may be a complication at delivery, increasing the risk for compression of the umbilical cord and aspiration of thick meconium (baby's first bowel movement).

What are the symptoms of oligohydramnios?

The following are the most common symptoms of oligohydramnios. However, each woman may experience symptoms differently. Symptoms may include:

  • Leaking of amniotic fluid when the cause is rupture of the amniotic sac

  • Decreased amount of amniotic fluid on ultrasound

The symptoms of the oligohydramnios may resemble other medical conditions. Always consult your physician for a diagnosis.


In addition to a complete medical history and physical examination, a diagnosis is usually made using ultrasound. Pockets of amniotic fluid can be measured and the total amount estimated. If it is between two and five centimeters, this is considered low Ultrasound can also show fetal growth, the structure of the kidneys and urinary tract, and detect urine in the fetal bladder. Doppler flow studies may be used to check the arteries in the kidneys.

Treatment for oligohydramnios:

Specific treatment for oligohydramnios will be determined by your physician based on:

  • Your pregnancy, overall health, and medical history

  • Extent of the condition

  • Your tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the condition

  • Your opinion or preference

Treatment for oligohydramnios may include:

  • Closely monitoring the amount of amniotic fluid and frequent follow-up visits with the physician

  • Amnioinfusion
    - instilling a special fluid into the amniotic sac to replace lost or low levels of amniotic fluid. Amnioinfusion is still experimental, but it may be offered during pregnancy in an attempt to help prevent pulmonary hypoplasia (underdeveloped lungs), or at delivery to help prevent compression of the umbilical cord.

  • Delivery. Often, this means weighing the risks of inducing labor versus leaving the baby in-utero until it reaches greater maturity

According to the American Journal of Obstetrics, pregnant women who find themselves diagnosed with oligohydramnios should pay particular attention to eating a balanced diet and receiving regular prenatal care

Complications list for Oligohydramnios:

The list of complications that have been mentioned in various sources for Oligohydramnios includes:

  • Miscarriage

  • Fetal loss


In order to prevent polyhydramnios or oligohydramnios, it would be necessary to prevent the underlying cause. Good control of maternal diabetes and the prevention of infections transmittable from mother to fetus are two approaches for a subset of cases, but, in general, prevention is not possible.



Dated 20 January 2009

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