Last revised by Jeremy Jones on 26 Sep 2021

Polyhydramnios refers to a situation where the amniotic fluid volume is more than expected for gestational age.

It is generally defined as:

It can occur in approximately 1-1.5% of pregnancies.

Polyhydramnios is associated with poor outcomes if present in combination with intrauterine growth restriction (IUGR); usually seen in aneuploidies 18,13, and 21.

The patient may clinically present as a large for dates uterus

Polyhydramnios occurs as a result of either increased production or decreased removal of amniotic fluid. The etiology of polyhydramnios can be due to a vast variety of maternal and fetal disorders. 

It is usually detected after 20 weeks (often 3rd trimester).

The potential causes of polyhydramnios are variable including:

This classification is general consensus based on common practices at the time of writing (July 2016) but this varies according to countries and gynecologist association guidelines.

Some classify the severity of polyhydramnios as 

  • mild: a single deepest pocket at 8-11 cm or amniotic fluid index (AFI) 25-30
  • moderate: a single deepest pocket at 12-15 cm or AFI 30.1-35
  • severe: single deepest pocket >16 cm or AFI >35

The prognosis is variable dependent on associated conditions. Usually minimal or no intervention is required for idiopathic mild uncomplicated cases. Options include:

  • improved maternal diabetes control
  • cesarian section if there is profound macrosomia
  • therapeutic amniocentesis/amnioreduction
  • indomethacin 9,10

The risk of the following obstetric complications is increased when polyhydramnios is present due to over-expansion of the uterus 13:

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Cases and figures

  • Case 1: with esophageal atresia
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  • Case 2: with duodenal atresia
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  • Case 3: increased AFI with gestational diabetes
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  • Case 4: with duodenal atresia
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  • Case 5
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