Polyhydramnios

This leaflet is to help you understand what Polyhydramnios is, what tests you need and the implication of having been diagnosed with polyhydramnios for you, your baby and your family.

What exactly is polyhydramnios or hydramnios?

Polyhydramnios is a condition where there is more amniotic fluid around your baby than usual. Amniotic fluid is the "water" that surrounds your baby in the womb and helps protect and support them during pregnancy. This is evaluated based on how far along the pregnancy is. It is a fairly common condition, affecting about 1–4% of all pregnancies. It usually appears in the second or third trimester and is often found during a routine ultrasound. In many cases, the cause is not known (idiopathic), and it is often mild. However, it can sometimes be linked to other conditions. Possible causes include:

• Idiopathic (unknown cause – about one third of cases)
• Gestational diabetes mellitus
• Fetal structural abnormalities (especially affecting the brain, stomach, or kidneys)
• Genetic conditions such as trisomy 21 (Down syndrome), trisomy 18, or trisomy 13
• Twin pregnancies with twin-to-twin transfusion syndrome (TTTS)
• Fetal anemia
• Rhesus isoimmunization
• Infections such as CMV, toxoplasmosis, rubella, parvovirus B19, syphilis, or Zika
• Maternal metabolic disorders (e.g., hypercalcemia)
• Rare inherited conditions (e.g., Bartter syndrome)
• Certain medications (e.g., maternal use of lithium)

More severe cases of polyhydramnios are more likely to have an underlying cause. Fetal anomalies associated with polyhydramnios include:

• Central nervous system defects (e.g., anencephaly, spina bifida)
• Gastrointestinal blockages (e.g., esophageal or duodenal atresia)
• Abdominal wall defects
• Heart conditions
• Skeletal disorders (e.g., dwarfism)
• Kidney and urinary tract anomalies
• Cleft lip and palate
• Chromosomal abnormalities (e.g., trisomy 21, 18, 13)

How can ultrasound help in the diagnosis of polyhydramnios?

Ultrasound is the main tool used to diagnose polyhydramnios. It allows your caregivers to measure the amount of amniotic fluid directly. Two key methods are used:

1. Deepest Vertical Pocket (DVP): The vertical depth of the largest pocket of fluid that does not contain the baby or the umbilical cord. A DVP greater than 8 cm suggests polyhydramnios.

2. Amniotic Fluid Index (AFI): The uterus is divided into four parts, and the deepest pocket of fluid in each part is measured. These measurements are added together. An AFI over 24 cm is considered polyhydramnios. 

Mild polyhydramnios is the most common and often resolves on its own. Moderate or severe polyhydramnios may require additional evaluation and monitoring.

Will I need any other tests?

Depending on the findings, your care provider may suggest:

• A glucose tolerance test to check for gestational diabetes
• Blood tests to check for infections (TORCH panel, Zika virus)
• Blood type and antibody screening for Rh incompatibility
• Genetic testing or amniocentesis if other fetal abnormalities are found

Is there anything else that ultrasound can tell me about polyhydramnios?

Ultrasound can also:

• Identify twin (or multiple) pregnancies and assess whether they share a placenta
• Detect possible fetal abnormalities
• Check your baby’s size and growth
• Evaluate for intrauterine growth restriction (IUGR – when the baby is smaller than expected)
• Detect fetal macrosomia (when the baby is larger than expected) 

What does it mean to have polyhydramnios?

Most women with mild polyhydramnios have normal pregnancies and healthy babies. However, polyhydramnios may increase the risk of:

• Premature labor or early rupture of the membranes
• Discomfort or trouble breathing due to the uterus being stretched
• Placental abruption (when the placenta detaches early)
• Umbilical cord prolapse (when the cord slips through the cervix before the baby)
• Postpartum bleeding
• Fetal malposition (e.g., breech)
• Higher chance of needing a cesarean delivery

What is the goal of treatment?

The goal is to monitor the baby and mother, relieve any discomfort, and manage the underlying cause if one was identified. Treatment depends on the severity:

• Mild cases often require no treatment beyond regular monitoring.
• Severe cases may need treatment to reduce the amount of amniotic fluid or prevent early delivery.

Common treatment options include:

• Medications: Indomethacin or sulindac (anti-inflammatory medications) may reduce fluid levels. These are generally only used before 32 weeks and require careful monitoring.
• Amnioreduction: Removal of some amniotic fluid via a needle (similar to amniocentesis). This is sometimes done to relieve symptoms or lower the risk of complications. In some cases, you may receive steroid injections to help your baby’s lungs mature if early delivery is likely.

What is the prognosis of polyhydramnios?

In mild, isolated cases, the outlook is excellent, and most pregnancies result in healthy babies. If polyhydramnios is linked to a condition affecting the baby or mother, the prognosis depends on that condition.

Are there things that ultrasound cannot tell me about polyhydramnios?

Ultrasound is a powerful tool, but not perfect. Factors like maternal body size, the baby’s position, and the examiner’s experience may affect accuracy. Some abnormalities may not be visible, and ultrasound cannot predict all outcomes. That’s why regular follow-up is important.

Are there any other important tips I should know? 

• Ask your provider about the experience level of the person doing your scan.
• Choose a center with experience in prenatal imaging and high-risk pregnancies.
• Don’t hesitate to ask questions and bring a support person to your appointments.
• Remember, many women with this diagnosis have healthy pregnancies.

 

Last updated: March 2025

 

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Polyhydramnios

 

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