[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Amniotic fluid disorders (polyhydramnios, oligohydramnios)

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# Amniotic fluid disorders (polyhydramnios, oligohydramnios)

Too much or too little fluid around the baby. Both can point to problems in the baby, the placenta or the mother and need closer monitoring.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Body of uterus](https://durgical.com/en/anatomy/body-of-uterus/)
- [Myometrium](https://durgical.com/en/anatomy/myometrium/)
- [Cervix](https://durgical.com/en/anatomy/cervix-of-uterus/)

## What it is

An abnormal volume of amniotic fluid for gestational age. Polyhydramnios is an excess (amniotic fluid index above about 24 cm or a deepest pocket of 8 cm or more). Oligohydramnios is a deficit (amniotic fluid index of 5 cm or less, or a deepest pocket under 2 cm). In the second half of pregnancy the fluid comes mainly from fetal urine and lung fluid and is removed by fetal swallowing.

## Who gets it

Each affects roughly 1 to 2 percent of pregnancies. Mild late polyhydramnios is often idiopathic or due to maternal diabetes; oligohydramnios is most common near or after term and after rupture of membranes. In Colombia, rising rates of gestational diabetes add to the cases of polyhydramnios.

## Causes

- Polyhydramnios: maternal diabetes (fetal polyuria)
- Polyhydramnios: impaired fetal swallowing or gut obstruction (oesophageal or duodenal atresia, anencephaly, neuromuscular disease)
- Polyhydramnios: multiple pregnancy (TTTS recipient), hydrops fetalis, fetal anaemia, infections
- Oligohydramnios: rupture of membranes (most common)
- Oligohydramnios: placental insufficiency (preeclampsia, growth restriction, post-term pregnancy)
- Oligohydramnios: fetal renal agenesis or urinary tract obstruction (posterior urethral valves)

## Risk factors

- Pre-existing or gestational diabetes
- Multiple pregnancy, especially monochorionic
- Hypertensive disorders of pregnancy
- Pregnancy beyond 41 weeks
- Fetal structural or chromosomal anomalies
- Certain maternal drugs (for example ACE inhibitors and NSAIDs reduce fetal urine output)

## Pathophysiology

Fluid volume reflects the balance between production (fetal urine, lung secretions) and removal (fetal swallowing, absorption across membranes). Anything that increases fetal urine or blocks swallowing raises the volume; anything that lowers fetal kidney perfusion or urine output, or lets fluid leak out, reduces it. In placental insufficiency the fetus redirects blood to the brain and away from the kidneys, so oligohydramnios is a sign of chronic hypoxia. Prolonged oligohydramnios in the second trimester compresses the fetus and prevents lung expansion, causing pulmonary hypoplasia and limb and facial deformities (Potter sequence).

## Classification

- Polyhydramnios: mild, moderate or severe by fluid measurement
- Oligohydramnios: by amniotic fluid index or deepest vertical pocket
- Anhydramnios: no measurable fluid

## Symptoms and signs

- Polyhydramnios: uterus larger than expected, tense [abdomen](https://durgical.com/en/anatomy/region/abdomen/), breathlessness, difficulty feeling the fetus
- Oligohydramnios: uterus smaller than expected, fetal parts easily felt
- Leakage of fluid from the [vagina](https://durgical.com/en/anatomy/vagina/) when membranes have ruptured
- Reduced fetal movements

## Red flags

- Sudden gush of fluid with a non-engaged presenting part (risk of cord prolapse)
- Oligohydramnios with growth restriction or abnormal Doppler
- Severe polyhydramnios with maternal breathlessness or preterm contractions
- Reduced fetal movements or abnormal fetal heart rate

## Diagnosis

**Clinical**
Suspected when fundal height does not match gestational age; confirmed by ultrasound. The cause is then sought in the fetus, the placenta and the mother.

**Tests**
Glucose tolerance test for diabetes; tests for infections and red-cell antibodies in polyhydramnios; tests for ruptured membranes (pH, ferning) in oligohydramnios; fetal karyotype by amniocentesis when anomalies are present.

**Imaging**
Ultrasound with amniotic fluid index or deepest vertical pocket, detailed fetal anatomy scan ([stomach](https://durgical.com/en/anatomy/stomach/) bubble, [kidneys](https://durgical.com/en/anatomy/kidney/) and bladder), fetal growth and umbilical and [middle cerebral artery](https://durgical.com/en/anatomy/middle-cerebral-artery/) Doppler.

## Differential diagnosis

- Wrong dates
- Multiple pregnancy
- Fetal macrosomia or growth restriction
- Uterine fibroids
- Urinary incontinence mistaken for leaking fluid

## Goal of treatment

Find and treat the underlying cause, watch fetal wellbeing closely, relieve maternal symptoms, and choose the safest moment and place for delivery.

## Treatment

**Follow-up**
Serial ultrasound of fluid and growth, nonstress tests and biophysical profile; delivery in a hospital with neonatal care.

**Medical**
Optimise glucose control in diabetes; in selected severe polyhydramnios before about 32 weeks a prostaglandin inhibitor (indometacin) may be used for a short time to reduce fetal urine, with fetal ductus monitoring.

**Procedure**
Amnioreduction (draining fluid) for severe symptomatic polyhydramnios; amnioinfusion in labour is used in some settings for oligohydramnios with cord compression.

**Surgical**
Delivery (induction or caesarean section) when oligohydramnios occurs at or near term or with signs of fetal compromise.

**Follow-up**
Teach the woman to report fluid leakage and reduced movements; after rupture with polyhydramnios, check for cord prolapse and monitor the fetal heart rate.

## Complications

- Polyhydramnios: preterm labour, malpresentation, cord prolapse, placental abruption on rupture, postpartum haemorrhage
- Oligohydramnios: cord compression and fetal distress in labour, meconium aspiration
- Pulmonary hypoplasia and Potter sequence with early severe oligohydramnios
- Higher caesarean section and perinatal mortality rates

## Prognosis

Mild idiopathic polyhydramnios and isolated oligohydramnios at term usually end well with monitoring. Outlook is worse when the cause is a fetal anomaly, placental insufficiency or when severe oligohydramnios starts in the second trimester.

## Prevention

- Early diagnosis and control of diabetes in pregnancy
- Avoiding ACE inhibitors, angiotensin receptor blockers and prolonged NSAIDs in pregnancy
- Fundal height measurement at every antenatal visit

## Test yourself

Think of the answer, then tap the question to see it.

## Which maternal condition is the classic cause of polyhydramnios?

Poorly controlled diabetes (fetal polyuria).

## Which fetal gastrointestinal anomaly can cause polyhydramnios?

Oesophageal or duodenal atresia (fetus cannot swallow or pass the fluid).

## What is the most common cause of oligohydramnios?

Rupture of membranes.

## Which fetal lung complication follows severe early oligohydramnios?

Pulmonary hypoplasia (part of the Potter sequence).

## What should be checked immediately after membranes rupture in polyhydramnios?

Umbilical cord prolapse and the fetal heart rate.

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## Related conditions

- [Gestational diabetes mellitus](https://durgical.com/en/conditions/gestational-diabetes-mellitus/)
- [Multiple pregnancy and twin–twin transfusion syndrome](https://durgical.com/en/conditions/multiple-pregnancy-and-twin-twin-transfusion-syndrome/)
- [Premature rupture of membranes (PROM and PPROM)](https://durgical.com/en/conditions/premature-rupture-of-membranes/)
- [Fetal growth restriction](https://durgical.com/en/conditions/fetal-growth-restriction/)
- [Post-term pregnancy](https://durgical.com/en/conditions/post-term-pregnancy/)
- [Preeclampsia](https://durgical.com/en/conditions/preeclampsia/)
- [Esophageal atresia and tracheoesophageal fistula](https://durgical.com/en/conditions/esophageal-atresia-and-tracheoesophageal-fistula/)
- [Duodenal and intestinal atresia](https://durgical.com/en/conditions/duodenal-and-intestinal-atresia/)
- [Congenital kidney anomalies (horseshoe kidney, renal agenesis)](https://durgical.com/en/conditions/congenital-kidney-anomalies/)
- [Rh alloimmunisation in pregnancy](https://durgical.com/en/conditions/rh-alloimmunisation-in-pregnancy/)
- [Umbilical cord prolapse](https://durgical.com/en/conditions/umbilical-cord-prolapse/)
- [Placental abruption](https://durgical.com/en/conditions/placental-abruption/)
- [Preterm labour and birth](https://durgical.com/en/conditions/preterm-labour-and-birth/)
- [Intrapartum fetal compromise (non-reassuring fetal status)](https://durgical.com/en/conditions/intrapartum-fetal-compromise/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Amniotic fluid](https://medlineplus.gov/ency/article/002220.htm) (MedlinePlus (U.S. National Library of Medicine), 2024); [Polyhydramnios](https://medlineplus.gov/ency/article/003267.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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Source: https://durgical.com/en/conditions/amniotic-fluid-disorders/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/amniotic-fluid-disorders/