Oligohydramnios is a deficient volume of amniotic fluid; it is associated with maternal and fetal complications. Diagnosis is by ultrasonographic measurement of amniotic fluid volume. Management involves close monitoring and serial ultrasonographic assessments.
The volume of amniotic fluid cannot be safely measured directly, except perhaps during cesarean delivery. Thus, deficient fluid is defined indirectly using ultrasonographic criteria, typically the amniotic fluid index (AFI). The AFI is the sum of the vertical depth of fluid measured in each quadrant of the uterus. The normal AFI ranges from 5 to 25 cm; values < 5 cm indicate oligohydramnios.
Causes of oligohydramnios include the following:
Complications of oligohydramnios include the following:
Risk of complications depends on how much amniotic is present and what the cause is.
Symptoms and Signs
Oligohydramnios itself tends not to cause maternal symptoms other than a sense of decreased fetal movement. Uterine size may be less than expected based on dates. Disorders causing or contributing to oligohydramnios may cause symptoms.
Oligohydramnios may be suspected if uterine size is less than expected for dates or if fetal movements are decreased; it may also be suspected based on incidental ultrasonographic findings. However, qualitative estimates of amniotic fluid volume tend to be subjective. If oligohydramnios is suspected, amniotic fluid should be assessed quantitatively using the AFI.
Identification of cause:
If oligohydramnios is diagnosed, clinicians should check for possible causes, including premature rupture of membranes. Comprehensive ultrasonographic examination is done to check for fetal malformations and any evident placental causes (eg, abruptio placentae).
Clinicians can offer amniocentesis and fetal karyotyping, particularly if ultrasonography suggests fetal malformations or aneuploidy.
If uteroplacental insufficiency is suspected, the umbilical artery is assessed using Doppler ultrasonography.
Ultrasonography should be done at least once every 4 wk (every 2 wk if growth is restricted) to monitor fetal growth. The AFI should be measured at least once/wk. Most experts recommend fetal monitoring with nonstress testing or biophysical profile at least once/wk and delivery at term. However, this approach has not been proved to prevent fetal death. Also, optimal time for delivery is controversial and can vary based on patient characteristics.
Last full review/revision January 2014 by Antonette T. Dulay, MD
Content last modified January 2014