If your health care provider suspects polyhydramnios, he or she will do a fetal ultrasound. This test uses high-frequency sound waves to produce images of your baby on a monitor.
If the initial ultrasound shows evidence of polyhydramnios, your health care provider may do a more detailed ultrasound. He or she will estimate the volume of amniotic fluid by measuring the deepest pocket in four specific parts of your uterus. The sum of these measurements is the amniotic fluid index (AFI). An AFI of 25 centimeters or more indicates polyhydramnios. Your health care provider will also use a detailed ultrasound to diagnose or rule out birth defects and other complications.
You may need additional tests as well, including:
- Amniocentesis. Amniocentesis is a procedure in which a sample of amniotic fluid — which contains fetal cells and various chemicals produced by the baby — is removed from the uterus for testing.
- Glucose challenge test. The glucose challenge test is a screening test for a type of diabetes that develops during pregnancy (gestational diabetes). After an overnight fast, you drink a syrupy glucose solution. Your blood sugar level will be checked every hour for a period of three hours. If at least two of the readings are higher than normal, you'll be diagnosed with gestational diabetes.
- Karyotype. Karyotype testing is used to screen the baby's chromosomes for abnormalities. The cells needed for testing can be taken from a sample of amniotic fluid during amniocentesis or a small piece of tissue from the placenta during a test called chorionic villus sampling.
If you're diagnosed with polyhydramnios, your health care provider will closely monitor your pregnancy, possibly with weekly ultrasounds to measure your level of amniotic fluid. Your health care provider may also do regular tests to check on your baby's health, including:
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- Nonstress test. This test checks how your baby's heart rate reacts when your baby moves. During the test, you'll wear a special device on your abdomen to measure the baby's heart rate. You may be asked to eat or drink something to make the baby active. A buzzer-like device also may be used to wake the baby and encourage movement.
- Biophysical profile. This test combines an ultrasound with a nonstress test to provide more information about your baby's breathing, tone and movement, as well as the volume of amniotic fluid in your uterus.
- Doppler ultrasound. This specialized type of ultrasound can provide details about your baby's circulation.
- Beloosesky R, et al. Polyhydramnios. http://www.uptodate.com/home. Accessed July 29, 2014.
- Goh AY, et al. Review of maternal and perinatal outcomes for women with polyhydramnios. Archives of Diseases in Childhood Fetal and Neonatal Edition. 2014;99(suppl):A1.
- Polyhydramnios. March of Dimes. http://www.marchofdimes.com/pregnancy/polyhydramnios.aspx. Accessed July 31, 2014.
- Cunningham FG, et al. Williams Obstetrics. 23rd ed. New York, N.Y.: The McGraw-Hill Companies; 2010. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=46. Accessed July 31, 2014.
- DeCherney AH, et al. Current Diagnosis & Treatment: Obstetrics & Gynecology. 11th ed. New York, N.Y.: The McGraw-Hill Companies; 2013. http://accessmedicine.mhmedical.com/book.aspx?bookid=498. Accessed July 31, 2014.