Polyhydramnios and Oligohydramnios Workup

Updated: Sep 20, 2017
  • Author: Brian S Carter, MD, FAAP; Chief Editor: Dharmendra J Nimavat, MD, FAAP  more...
  • Print

Approach Considerations

In the setting of polyhydramnios or oligohydramnios, testing of the infant is recommended, depending on the results of postnatal evaluation of the infant. Such evaluation may include chromosome testing, testing for evidence of congenital infection, ultrasonography of the genitourinary tract, and appropriate radiologic evaluation of the gastrointestinal tract. Electrocardiography and echocardiography may also be indicated.

Histologic examination of the placenta may be helpful in determining the cause of the polyhydramnios or oligohydramnios.


Laboratory Studies

If premature delivery is anticipated with either oligohydramnios or polyhydramnios, the amniotic fluid lamellar body count, lecithin-sphingomyelin (L:S) ratio, and phosphatidylglycerol (PG) concentration are helpful in determining the maturity of the fetal lungs and, therefore, in assessing the likelihood of respiratory distress syndrome.


Obtain glucose tolerance testing for mothers with suspected type 2 diabetes mellitus.

If fetal hydrops is present, immunologic and fetal infection need to be investigated. This should include screening for maternal antibodies to D, C, Kell, Duffy, and Kidd antigens to determine maternal antibody production against the fetal red blood cells. Infections of the fetus include cytomegalovirus (CMV), toxoplasmosis, syphilis, and parvovirus B19. The investigation should include the following studies:

  • Venereal Disease Research Laboratories (VDRL) test to screen for syphilis

  • Immunoglobulin G (IgG) and IgM titers to evaluate for exposure to rubella, CMV, toxoplasmosis, and parvovirus

  • A test for congenital viruses in the amniotic fluid using polymerase chain reaction (PCR)

  • Kleihauer-Betke test to evaluate fetal-maternal hemorrhage

  • Hemoglobin Bart in patients of Asian descent (who may be heterozygous for alpha-thalassemia)

  • Fetal karyotyping for trisomy 21, 13, and 18


Premature rupture of membrane (PROM)  is the most common cause of oligohydramnios; therefore, obtain available tests to confirm or exclude this condition. Maternal substance abuse and certain medications (eg, nonsteroidal anti-inflammatory drugs [NSAIDs], angiotensin-converting enzyme inhibitors [ACEI]) can also cause oligohydramnios.

Test for systemic lupus erythematosus (SLE), which causes immune-mediated infarcts in the placenta as well as placental insufficiency.

Evaluate for pregnancy-induced hypertension (PIH) and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. Test for elevated blood pressure, proteinuria, elevated uric acid levels, increased liver function test results, and low platelet count.


Imaging Studies

Prenatal ultrasonography and polyhydramnios

Evaluate fetal swallowing. A decrease in fetal deglutition occurs in anencephaly, trisomy 18, trisomy 21, muscular dystrophy, and skeletal dysplasia.

Evaluate the fetal anatomy; assess for diaphragmatic hernia, lung masses, and the absence of the stomach bubble (which is associated with esophageal atresia). The double-bubble sign or a dilated duodenum suggests the possibility of duodenal atresia.

Test for fetal arrhythmias and malformations that result in cardiac failure and hydrops.

An abnormally large abdominal circumference may be observed with ascites and hydrops fetalis.

A macrosomic fetus is observed in association with poorly controlled maternal diabetes.

Assess the blood flow velocity in the fetal middle cerebral artery for fetal anemia.

Prenatal ultrasonography and oligohydramnios

Perform serial measurements of the amniotic fluid index during the pregnancy. If the mother is in the third trimester and if the volume is less than 8 cm, suspect oligohydramnios. Levels below 5 cm indicate significant oligohydramnios.

Visualize the fetal kidneys, collecting system, and bladder. If these are normal, suspect the chronic leakage of amniotic fluid or pregnancy-induced hypertension.

Assess fetal growth. If premature rupture of the membrane or urinary tract anomalies are absent, consider placental insufficiency and intrauterine growth restriction.

Uterine artery Doppler study findings may aid in the diagnosis of placental insufficiency.

Postnatally, evaluate organ systems likely to be involved on the basis of the pregnancy history and results of other prenatal evaluations. For more information, see Oligohydramnios Imaging.

Color Doppler ultrasonography

In a study that used color Doppler ultrasonography in addition to grayscale ultrasonography to evaluate 428 women for detection of amniotic fluid disturbances and perinatal outcomes, investigators did not find an increased detection of pregnancies at risk for adverse intrapartum or perinatal outcomes with this added evaluation. [16] However, color Doppler ultrasonography did appear to result in lower estimates of amniotic fluid volume (ie, overdiagnosis of low amniotic fluid volume).




Reductive amniocentesis may be performed and has contributed to prolonged pregnancy in patients who are severely affected by hydramnios. [17] This procedure can reduce the risk of preterm labor, premature rupture of the membrane (PROM), umbilical cord prolapse, and placental abruption. However, if too much fluid is removed, placental abruption may occur. Other risks of the procedure include infection, bleeding, and trauma to the fetus.

Laser ablation of placental vessels may be effective in cases of twin-to-twin transfusion syndrome, performed at highly specialized centers.


The transabdominal instillation of indigo carmine may be used to evaluate for PROM.

The transcervical instillation of isotonic sodium chloride solution (ie, amnioinfusion) at the time of delivery reduces the risk of cord compression, fetal distress, and meconium dilution. It also reduces the potential need for cesarean delivery.