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 (9.8 inches) 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 gestational diabetes, a type of diabetes that develops during pregnancy. 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 or the placenta during amniocentesis or 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 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.
- Contraction stress test. This test checks how the baby's heart reacts when your uterus contracts. To make your uterus contract, you may be asked to stimulate your nipples — or your health care provider may give you an injection of the synthetic version of the hormone oxytocin. This test isn't often used with polyhydramnios due to concerns about preterm labor.
- Beloosesky R, et al. Polyhydramnios. http://www.uptodate.com/home/index.html. Accessed Oct. 5, 2011.
- Cunningham FG, et al. Disorders of amniotic fluid volume. In: Cunningham FG, et al. Williams Obstetrics. 23rd edition. New York, N.Y.: McGraw-Hill Companies; 2010. http://www.accessmedicine.com/content.aspx?aID=6026246. Accessed Oct. 6, 2011.
- Polyhydramnios. March of Dimes. http://www.marchofdimes.com/pregnancy/complications_polyhydramnios.html. Accessed Oct. 6, 2011.
- Ross MG, et al. National institute of child health and development conference summary: Amniotic fluid biology — basic and clinical aspects. The Journal of Maternal-Fetal Medicine. 2001;10:2.
- Gilbert WM. Amniotic fluid disorders. In: Gabbe SG, et al. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa.: Churchill Livingstone Elsevier; 2007. http://www.mdconsult.com/das/book/body/208746819-4/0/1528/0.html. Accessed Oct. 6, 2011.
- Strehlow SL, et al. Diabetes mellitus & pregnancy. In: DeCherney AH, et al. Current Diagnosis & Treatment Obstetrics & Gynecology. 10th ed. New York, N.Y.: The McGraw-Hill Companies; 2007. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=9. Accessed Oct. 10, 2011.
- Carlo WA. High-risk pregnancies. In: Kliegman RM, et al. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/208746819-6/0/1608/0.html. Accessed Oct. 11, 2011.
- Screening for birth defects. American College of Obstetricians and Gynecologists. http://www.acog.org/publications/faq/faq165.cfm. Accessed Oct. 10, 2011.
- Special tests for monitoring fetal health. American College of Obstetricians and Gynecologists. http://www.acog.org/publications/faq/faq098.cfm. Accessed Oct. 10, 2011.