Considerations

Amniotic fluid is a clear, slightly yellowish liquid that surrounds the unborn baby (fetus) during pregnancy. The amniotic fluid constantly moves as the baby swallows and breathes in the fluid, and then releases it through urine.

While in the womb, the baby floats in the amniotic fluid. Amniotic fluid surrounds and cushions the infant throughout pregnancy. The amount of amniotic fluid is greatest at around 34 weeks of pregnancy.

The amniotic fluid helps:

• The developing baby move in the womb, which allows for proper bone growth
• The lungs to develop properly
• Keep a relatively constant temperature around the baby, protecting from heat loss
• Protect the baby from outside injury by cushioning sudden blows or movements

Causes

Polyhydramnios can occur if the developing baby does not swallow and absorb amniotic fluid in normal amounts. This can happen if the baby has certain health problems, including:

• Gastrointestinal disorders, such as duodenal atresia, esophageal atresia, gastroschisis, and diaphragmatic hernia
• Brain and nervous system problems, such as anencephaly and myotonic dystrophy
• Achondroplasia
• Beckwith-Wiedemann syndrome

It can also happen if the mom has poorly controlled diabetes.

Polyhydramnios may also be due to increased fluid production, which occurs with:

• Certain lung disorders in the baby
• Multiple pregnancy (for example, twins or triplets)
• Hydrops fetalis in the baby

Sometimes, no specific cause for polyhydramnios is found.

When to Contact a Medical Professional

Call your health care provider if you are pregnant and notice that your belly is getting large very quickly.

What to Expect at Your Office Visit

This condition is discovered during pregnancy. You doctor or nurse measures the size of your belly at every visit. This tells them your womb (uterus) size. If your womb is growing faster than expected, or it is larger than normal for your baby's gestational age, the doctor or nurse may:

• Have you come back sooner than normal to check it again
• Perform an ultrasound

If the health care provider finds a birth defect, you may need an amniocentesis to test for a genetic defect.

Mild polyhydramnios that shows up in the latter part of pregnancy does not often cause serious problems.

More severe polyhydramnios may be treated with medications or by having extra fluid removed.

Women with polyhydramnios are more likely to go into early labor. The baby will be delivered in a hospital with specialists who can provide immediate evaluation and treatment.

References

Carlo WA. High-risk pregnancies. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 89.

Cunningham FG, Leveno KJ, Bloom SL, et al. Disorders of amnionic fluid volume. In: Cunningham FG, Leveno KL, Bloom SL, et al, eds. Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010:chap 21.

Gilbert WM. Amniotic fluid disorders. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa: Churchill Livingstone; 2007:chap 31.

Updated: 4/19/2012

Reviewed by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.