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Immune Hydrops

The abnormal collection of fluid in more than one area of the fetal body, such as ascites and pleural effusion, is termed hydrops. In immune hydrops, excessive and prolonged hemolysis causes anemia, which stimulates marked erythroid hyperplasia of the bone marrow as well as extra medullar hematopoiesis in the spleen and liver with eventual hepatic dysfunction.

  1. The data from several studies indicate that in most cases, the degree and duration of anemia is the major factor causing and influencing the severity of ascites. Secondary factors include hypoproteinemia caused by liver dysfunction and capillary endothelial leakage resulting from tissue hypoxia. Both of these factors lead to protein loss and decreased colloid oncotic pressure, and make the hydrops worse.
  2. Hydropic changes in the placenta, leading to placentomegaly, can cause preeclampsia. Because the preeclamptic mother develops severe edema mimicking that of the fetus, this development is referred to as the mirror
  3. USG findings in case of hydrops fetalis:
    1. Ground glass placenta
    2. Pleural/pericardial effusion
    3. Ascites
    4. Hepatosplenomegaly
    5. Scalp edema (Buddha sign)
    6. Increase in peak systolic velocity (PSV) >1.5 MOM in middle cerebral artery on color Doppler.



When the mother is Rh negative and the father is positive:

  1. Rh titer or indirect Coombs' test (ICT) should be done on maternal serum at 20, 24 and 28 weeks.
  2. If ICT is negative at 28 weeks then one dose of anti-D immunoglobulin (300 μg) is given prophylactically to all D-negative women at about 28 weeks, and a second dose is given after delivery if the infant is D-positive.
  3. If the ICT is positive or Rh titer is above the cutoff, then amniocentesis should be done.
  4. Amniotic fluid evaluation: When fetal blood cells undergo hemolysis, breakdown pigments, mostly bilirubin, are present in the supernatant of amniotic fluid. The amount of amniotic fluid bilirubin correlates roughly with the degree of hemolysis and thus indirectly predicts the severity of the fetal anemia. Because the amniotic fluid bilirubin level is low compared with serum levels, the concentration is measured by a continuously recording spectrophotometer and is demonstrable as a change in absorbance at 450 nm, referred to as AOD450, and the value is plotted on Liley's graph.

Results fall into one of the 3 Zones of Liley curve




Zone 1 (i.e. fetus is mildly affected)

• Repeat amniocentesis at 4 weeks and delivery at term 38-40 weeks

Zone 2 (i.e. fetus is moderately affected) In the lower zone 2-anticipated Hb level is 11-13.9 mg/dl, in the upper zone 2 it is 8-10.9g/dl

• Repeat amniocentesis at 1-2 weeks

Zone 3 (i.e. fetus is severely affected) anticipated Hb = < 8 g/dl

• Intrauterine transfusion if preterm or delivery at 34 weeks if fetus is salvageable

  1. Optical density values in zone 1 indicate a fetus that will have only mild disease. Amniocentesis should be repeated in 3-4 weeks.
  2. In zone 2, the fetus is at moderate risk. In low zone 2, the expected fetal hemoglobin concentration is between 11.0 and 13.9 g/dl, whereas in upper zone 2, the anticipated hemoglobin level ranges from 8.0 to 10.9 g/dl.
  3. Amniocentesis should be repeated after 1 week.
  4. Values in zone 3 indicate a severely affected fetus with a hemoglobin level of less than 8.0 g/dl, and, without therapy, death is predicted within 7-10 days value in zone 3 demands immediate fetal red blood cell transfusion (intra-uterine transfusion) or delivery.

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