Birth Definitions

Oligohydramnios Definition


Oligohydramnios, also known as low amniotic fluid, is a condition that can occur during pregnancy. It is characterized by a decrease in the amount of amniotic fluid surrounding the fetus. Amniotic fluid is important for fetal development and helps to protect the fetus from infection and trauma. It can occur at any point during pregnancy, but is most common in the third trimester.


There are a number of different causes of oligohydramnios, including:

  1. Placental insufficiency: This occurs when the placenta does not provide enough blood and oxygen to the fetus. This can be due to a number of factors, including placental abruption, preeclampsia, or diabetes.
  2. Leaking of amniotic fluid: This can happen due to rupture of membranes or other problems with the placenta or umbilical cord.
  3. Decreased production of amniotic fluid: This can be due to certain conditions such as diabetes or preeclampsia.
  4. Excessive urine output by the fetus: This can be due to genetic conditions such as polycystic kidney disease.
  5. Reduced fetal urine output: This can be due to decreased renal function, or blockage of the urinary tract. 
  6. Preterm labor: This may cause the rupture of membranes and consequent loss of amniotic fluid. 
  7. Postdate pregnancy: Amniotic fluid levels naturally decrease as pregnancy progresses. 
  8. Twins or multiple gestations: There may be competition between fetuses for available amniotic fluid. 
  9. Chorioamnionitis: This is an infection of the chorion (the outermost membrane) and/or amnion (the innermost membrane). 
  10. Abnormal uteroplacental blood flow: This can be due to various conditions, such as preeclampsia or placental insufficiency. 
  11. Fetal anomalies: Certain birth defects, such as Potter syndrome (a condition characterized by oliguria), can cause oligohydramnios.

Risk Factors and Complications

Risk factors for oligohydramnios include:

  • Previous history of oligohydramnios in a previous pregnancy
  • Maternal age over 35 years old
  • Smoking during pregnancy
  • Advanced maternal age (>35 years) 
  • Male fetus 
  • Small for gestational age fetus 
  • History of oligohydramnios in a previous pregnancy 
  • Family history of congenital anomalies 
  • Excessive use of tobacco, alcohol, or illicit drugs during pregnancy

Complications associated with oligohydramnios include: 

  • Preterm labor: Oligohydramnios can cause the cervix to dilate prematurely, leading to preterm labor. 
  • Possible fetal growth restriction: Low levels of amniotic fluid can lead to decreased fetal movement and possible growth restriction. 
  • Increased risk for infection: Without adequate levels of amniotic fluid, the fetus is at increased risk for infection.

Related Terms

Some terms that are closely associated with oligohydramnios include: 

  • Amnion: The innermost of the two membranes that surround the fetus in utero. 
  • Amniotic fluid: The fluid that surrounds the fetus in utero, and is contained within the amnion. 
  • Anuria: A condition characterized by a complete absence of urine production. 
  • Chorioamnionitis: An infection of the chorion (the outermost membrane) and/or amnion (the innermost membrane). 
  • Fetal anomalies: Any congenital abnormality or birth defect. 
  • Potter syndrome: A condition characterized by oliguria, which is a decreased urine output.
  • Polyhydramnios: A condition where there are high levels of amniotic fluid.
  • Hydramnios: A condition where there is an abnormal accumulation of amniotic fluid.
  • Anhydramnios: A condition characterized by the absence of amniotic fluid.

This image shows how often the term ‘Oligohydramnios’ is used in relation to other, similar birth terms:

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