Low Amniotic Fluid Concerns

PregnancyOligohydramnios is the medical term for a condition occurring in some pregnancies in which the amount of amniotic fluid in the womb is too low. Amniotic fluid plays part in gestation and oligohydramnios can lead to major problems and complications that can result in birth defects and even miscarriages.

About Oligohydramnios

Amniotic fluid is a critical component of pregnancy and fetal development. In the early stages of pregnancy amniotic fluid is composed primarily of water. It fills the womb and surrounds the baby during pregnancy serving as a cushion and insulation. It also enables the baby to move around inside the womb which is important to early muscle and nerve development.

As the pregnancy progresses the amniotic fluid takes on a different composition and serves additional functions. The baby begins to inhale and swallow the amniotic fluid and which helps develop the lungs and digestive system. Once swallowed the amniotic fluid is "digested" by the baby's developing gastrointestinal system and the byproducts are regularly eliminated in fetal urine. By around week 20 amniotic fluid is less water and more fetal urine.

Levels of amniotic fluid vary somewhat depending on the mother, fetal weight, and stage of gestation. However, the volume of amniotic fluid should stay above certain minimum levels throughout the pregnancy. If the volume of amniotic fluid drops below minimum levels at any point during the pregnancy the condition is diagnosed as oligohydramnios.

Sonogram and ultrasound imaging allows amniotic fluid levels to be accurately measured during pregnancy with several different methods including measuring the depth of fluid pockets or through the amniotic fluid index (AFI). A diagnosis of oligohydramnios is made if there is no visible fluid 2-3 cm fluid pocket or AFI indicates fluid levels of less than 5 cm. Total fluid volume below 500 ml after week 32 is also considered oligohydramnios.

Low amniotic fluid levels occur in about 8% of pregnancies but oligohydramnios is only diagnosed in about 4 out of every 100 pregnancies. The condition is much more common in the final trimester but it does occur much earlier in some cases. When oligohydramnios occurs earlier in pregnancy it can be more problematic and potentially dangerous for the baby.

Causes of Oligohydramnios

There are number of condition and abnormalities that are known to cause to contribute to low amniotic fluid levels. Often oligohydramnios is causes by a combination of these conditions which include the following:

  • Placental Abnormalities: when the placenta is not functioning properly the supply of nutrients and blood to the fetus may be disrupted which can decrease amniotic fluid levels.
  • Birth Defects: certain congenital birth defects involving the baby's kidneys or urinary function can decrease the amount of fetal urine that the baby produces during pregnancy. During the 2nd half of gestation amniotic fluid is comprised mostly of fetal urine so this will lower fluid levels.
  • Leak in Fetal Membranes: low amniotic fluid levels can be the result of a leak in the fetal membranes allowing fluid to drip or gush out. This can be related to a tear or uterine rupture which is a very serious condition.
  • Maternal Health Condition: many cases of oligohydramnios are the result of the mother's health condition. Water from the mother is a key component of amniotic fluid so maternal dehydration is often a leading factor involved in low fluid levels. Maternal hypertension, preeclampsia and gestational diabetes are also known to contribute to low amniotic fluid.
Risks & Complications of Oligohydramnios

Amniotic fluid is very important for healthy fetal growth and development so abnormally low fluid levels can be harmful no matter when it occurs. However, the particular risks and potential complications from oligohydramnios vary depending on the stage of gestation when the condition occurs.

The risks and dangers of oligohydramnios are generally greater when the condition occurs earlier in pregnancy. Low amniotic fluid levels in the first half of pregnancy can result in developmental birth defects caused by pressure compression of the baby's organs as the develop inside the womb. Early onset oligohydramnios can also significantly increase the risk of miscarriage or stillbirth.

When oligohydramnios develops in the 2nd half of pregnancy the dangers to the baby are not as acute but still very real. Low amniotic fluid in later stages of gestation is known to cause numerous complications including: intrauterine growth restriction; early labor and premature birth. Oligohydramnios also makes vaginal delivery more problematic because it increases the risk of certain childbirth complications such as umbilical cord compression and umbilical cord prolapse.

Treatment & Management of Oligohydramnios

Options for medical treatment and/or management of oligohydramnios varying depending on how far along the pregnancy is. When the condition occurs early on in pregnancy options are much more limited because it may be too early to deliver the baby safely. The best doctors can do is monitor the baby's condition very closely until it has developed enough to consider early delivery. There are certain diagnostic tests such as fetal stress tests that can be used to see how the baby is developing and responding to the low amniotic levels. When oligohydramnios is diagnosed in the later stages of pregnancy the standard response is to plan for early delivery of the baby, usually as soon as possible.

There are handful of additional options doctors can use to treat and manage oligohydramnios. During labor and delivery an amnio-infusion can be done to infuse synthetic amniotic fluid into the mother's womb in preparation for vaginal delivery. The addition fluid will help surround and cushion the umbilical to lower the risk of cord compression and other problems. When oligohydramnios is related to maternal dehydration the mother may be give fluids through an IV drip to help rehydrate her and boost fluid levels.