Oligohydramnios is too little fluid in the amniotic sac. The amniotic sac is the “water bag” inside the womb that cushions and protects your baby. It also allows normal growth and development to occur. Normal amniotic fluid levels vary. The average volume during pregnancy is almost one liter at 36-37 weeks. Less than 10% of pregnant women develop oligohydramnios.

Low amniotic fluid can indicate a problem in the mother or the baby. It can also cause problems that vary depending on when in pregnancy oligohydramnios occurs.

Problems in the first half of pregnancy:

  • Higher risk of miscarriage
  • Compression of the baby, leading to birth defects
  • Lack of lung development
  • Increased risk of infection

Problems in the second half of pregnancy:

  • Reduced growth of baby
  • Induction of labor and delivery before 39 weeks (called preterm birth)
  • Fetal distress in labor, possibly leading to cesarean delivery (“C-section”)
  • Increased risk of infection

Fetus in Utero, Amniotic Fluid
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There are many known causes of oligohydramnios. However, sometimes a specific cause cannot be found. Conditions that can cause oligohydramnios include:

  • Birth defects (eg, neural tube defect)
  • A problem with the placenta (the tissue that supplies the baby with nutrients through the umbilical cord)
  • Tear in the amniotic sac (also called rupture of membranes)
  • Pregnancy continuing past the due date
  • Problems in the mother, such as dehydration, diabetes, or high blood pressure
  • Complication of medicines such as:
    • ACE inhibitor to manage blood pressure
    • Tocolytic medicine to reduce uterine contractions