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What is oligohydramnios?

Oligohydramnios occurs when a pregnant person has low amniotic fluid. Amniotic fluid is the watery substance that surrounds and protects your baby during development in the uterus. This condition is uncommon, affecting only about 4% of pregnant people.

Low amniotic fluid doesn’t always affect a developing baby, but it can. Generally, the earlier in the pregnancy that oligohydramnios occurs, the higher the risks to your baby.

Although oligohydramnios can occur at any point in pregnancy, it’s most common in the third trimester. It’s more likely if you are two or more weeks past your due date. This is because amniotic fluid naturally decreases after your due date.

What causes oligohydramnios?

Oligohydramnios often happens for no known reason. Known causes of this condition include:

  • Being pregnant with multiple babies
  • Carrying a pregnancy past your due date
  • Congenital (present at birth) conditions in the baby such as kidney or other urological abnormalities
  • Health conditions such as preeclampsia, high blood pressure or diabetes
  • Use of medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) or angiotensin-converting enzyme (ACE) inhibitors
  • Premature rupture of the membranes (PROM) when the amniotic sac breaks before labor
  • Problems with the placenta

What are the risks of oligohydramnios?

Oligohydramnios carries higher risks in the first and second trimesters. Low amniotic fluid early in pregnancy can increase the risk of:

  • Congenital conditions, especially those affecting the face or limbs
  • Facial and limb anomalies
  • Miscarriage
  • Placental problems, such as abruption
  • Poor fetal growth
  • Poor fetal lung growth
  • Preterm birth
  • Stillbirth

Oligohydramnios in the third trimester doesn’t usually lead to long-term problems. In rare cases, late-term oligohydramnios can cause:

  • A need for more intensive care
  • Higher chances of a congenital condition
  • Increased chance of cesarean section (C-section)
  • Joint problems, because the low amount of fluid restricts the baby’s movements
  • Meconium aspiration, when a baby inhales their first bowel movement
  • Need for labor induction
  • Slow fetal growth
  • Stillbirth or neonatal death
  • Umbilical cord squeezing

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