Red Cell Alloimmunization (Rh Alloimmunization.ppt

Red Cell Alloimmunization (Rh Alloimmunization,Red Cell Alloimmunization (Rh Alloimmunization,Red Cell Alloimmunization (Rh Alloimmunization.

1. Red Cell Alloimmunization (Rh
Alloimmunization
Berihu

2. Introduction
Alloimmunization refers to an immune response
(sensitization) to foreign antigens from another
human, most commonly occurring after pregnancy or
blood transfusions.
 The risk of developing severe reaction is proportional to
the antigen load, i.e. the more amount of antigen exposed,
the greater the risk for alloimmunization reactions to
occur.

3. …
Rh Alloimmunization is therefore, formation of
anti-red cell antibodies by a Rh negative (Rh-)
pregnant women who is exposed to Rh positive
(Rh+) fetus's RBC due to fetomaternal hemorrhage
(FMH).

4. Epidemiology
The prevalence of red cell alloimmunization in pregnancy
approximates 1 %.
 Most cases of severe fetal anemia requiring antenatal
transfusion are attributable to anti-D, anti-Kell, anti-c, or
anti-E alloimmunization.
The prevalence of D alloimmunization complicating
pregnancy ranges from 0.5 to 0.9 percent.

5. …
Alloimmunization is uncommon for the following reasons:
Low prevalence of incompatible erythrocyte antigens
Insufficient trans-placental passage of fetal antigens and maternal
antibodies
Maternal-fetal ABO incompatibility, which leads to rapid clearance
of fetal erythrocytes before they elicit an immune response
Variable antigenicity
Variable maternal immune response to the antigen

6. Group Systems
Currently, 36 different blood group systems and 360 erythrocyte
antigens are recognized by the International Society of Blood
Transfusion. (43 and 343 respectively on up-to-date 2022)
Clinically significant Blood group systems are: ABO, Rh
(CDE), Kell, Duffy, Kidd, etc...
At first Antenatal care, Blood grouping should be offered for
every pregnant woman even if the woman is aware of her status

7. ABO Blood Group System
Responsible for 4 major RBC phenotypes: A, B, O, and AB
It has 3 antigens A, B and H and 2 antibodies; anti-A and
anti-B
 Antibodies to ABO antigens generally appear in the blood
by 4 to 6 months of age following exposure to bacterial
antigens that are similar in structure to the A and B antigens
as the gut becomes colonized in early infancy.

8. …
ABO incompatibility can cause
Acute hemolytic transfusion reactions (AHTR),
Hemolytic disease of the fetus and newborn
(HDFN), and
Solid organ transplant rejection

9. Rh (CDE) Blood Group System
More than 45 serologically defined antigens have
been recognized within the Rh system.
The most common and clinically significant include
D, C, c, E, and e (there is no "d" antigen)
The D antigen is detectable on embryonic RBCs by
38 daysafter conception (i.e.5+3 weeks of gestation)

10. Phenotypes under Rh blood group system
Rh-positive - Individuals whose RBCs express the RhD antigen.
Approximately 40 % of RhD +ve individuals are homozygous for
the D antigen (DD); the remainders are heterozygous (Dd).
Since the Rh allele transmission is in an autosomal recessive
fashion, if the father is heterozygous the baby has a 50% chance of
being Rh -ve. But if father is homozygous the baby would always
be Rh +ve.

11. …
Rh-negative – Individuals whose RBCs do not
express the RhD antigen.
This phenotype is the result of either an absence
of the RHD gene or alterations in the RHD gene
resulting in gene inactivation.

12. …
The prevalence of the D antigen varies among
populations:
Africans – 4 to 6 %,
Indians – 5 %
Black or African Americans – 8 %,
White North Americans or Europeans – 15 %,
Chinese – 0.3%

13. …
Partial or weak D – Several D variants exist,
referred to as partial D, weak D, Rh mod, D (u), and
D (el).
In some cases, these cells may type as RhD-positive by
all available serologic reagents, and in some cases they
may not

14. Genetics of Rh system
Genes encoding for Rh surface antigen are found
on short arm of chromosome 1.
 Approximately 40% of Rh +ve individuals are
homozygous (DD) and the remainders are
heterozygous (Dd).

15. …
The allele of Rh is transmitted in an
autosomal recessive manner.
Therefore, if the father is heterozygous
the baby has a chance of 50% to be Rh -
ve.

16. Rh (CDE) Blood Group
Incompatibility
The CDE system includes five erythrocyte antigens:
C, c, D, E, and e.
The C, c, E, and e antigens have lower immunogenicity
than the D antigen but can cause hemolytic disease.
The prevalence of D alloimmunization complicating
pregnancy ranges from 0.5 to 0.9 percent

17. …
Unless the pregnant woman is sensitized before pregnancy,
the 1st pregnancy remains unaffected but the fetal affection
increases with subsequent pregnancies i.e the 3rd pregnancy
is more affected than 2nd pregnancy
This is because of the repeated re-exposure to Rh+ RBC
resulted in greater immune response- anamnestic reaction

18. …
•Does every Rh -ve women who delivered Rh +ve
baby develop Rh alloimmunization if not given
anti-D Ig prophylaxis? ... No.

19. …
Without anti-D Ig prophylaxis, an Rh-ve woman delivered
of an Rh +ve, ABOcompatible newborn has only a 16%
(13% on gabby 7th edition) likelihood of developing
alloimmunization.
 2% will become sensitized by the time of delivery,
7 % by 6 months postpartum,
7 % will be “sensibilized”—producing detectable
antibodies only in a subsequent pregnancy

20. …
If there is ABO incompatibility, the D alloimmunization
risk decreases to 2 %because erythrocyte destruction of
incompatible cells limits sensitization
With immunoprophylaxis, at 28th week and postpartum,
however, the alloimmunization risk may be reduced to <0.2
% (0.1 - 0.3%)

21. …
The advent of the routine administration of antenatal and
postpartum Anti-D Ig has resulted in a marked reduction in
cases of red cell alloimmunization secondary to the RhD
antigen and a shift to other red cell antibodies associated
with HDFN has occurred as a result of the decreasing
incidence of RhD alloimmunization

22. …
Anti-E alloimmunization is the most common, but
the need for fetal or neonatal transfusions is greater
with anti-c alloimmunization than with anti-E or
anti-C.
Anti-c antibody should be considered equivalent to
anti-D regarding its potential to cause HDFN

23. Grandmother effect theory
In virtually all pregnancies, small amounts of maternal blood
enter the fetal circulation. An Rh-negative female fetus exposed
to maternal Rh-positive red cells might develop sensitization,
and later might produce anti-D antibodies before or during
pregnancy. This mechanism is called the grandmother effect
because the fetus in the current pregnancy is jeopardized by
maternal antibodies that were initially provoked by his or her
grandmother’s erythrocyte

24. Alloimmunization to Minor
Antigens
Kell Alloimmunization may develop more rapidly and may be more
severe than with sensitization to D and other blood group antigens.
Unlike the case of other hemolytic antibodies, fetal anemia due to Kell (anti-
K1) sensitization is thought to be secondary to not only
hemolytic but also to suppression of fetal erythropoiesis. This
is because Kell antibodies attach to erythrocyte precursors in the
fetal bone marrow and thereby impair the normal hemopoietic
response to anemia.

25. …
With fewer erythrocytes produced, there is less hemolysis,
and thus severe anemia may not be predicted by the maternal
Kell antibody titer.
Given the potential for severe anemia, the ACOG has
recommended
ultrasound surveillance regardless of titer
antibody titers not be used to monitor Kell-sensitized
pregnancies

26. …
Transfusion history is important, as nearly 90 % of Kell
sensitization cases result from transfusion with Kell-positive
blood usually as a result of postpartum hemorrhage in a
previous pregnancy.
Because 92% of individuals are Kell negative, the initial
management of the K1-sensitized pregnancy should entail
paternal red cell typing and genotype testing

27. …
At present, prophylactic Ig preparations to prevent
other forms of red cell alloimmunization such as
anti-K1 do not exist.

28. Management of Pregnancy in Rh
Negative Women

29. …

30. Management of ICT Negative Pregnancy
/Prevention of Sensitization /
 Rh negative women with negative anti-D Antibody Screen
(ICT) are candidates for Anti-D Ig at:
 28 weeks of gestation – RAADP.
After Antepartum events associated with an increased
FMH
After delivery of Rh positive neonates – Postpartum
prophylaxis

31. Routine Antenatal Anti-D prophylaxis
(RAADP)
After initial ICT screening become negative, ideally repeat ICT
every 4 weeks until 28th week of Gestation and give Anti-D if
ICT remains negative.
The issue of repeating an antibody screen after initial negative result is
controversial and ACOG leaves the decision to repeat the
antibody screen up to the obstetric provider.

32. …
Practically we repeat ICT at 28th week of gestation and
provide IM injection of 300 mcg (1500 IU) anti-D IgG
prophylaxis if the ICT result is negative
Why at 28 weeks? Risk of FMH is more in the 3rd Trimester
and exogenously administered anti-D Ig protective
effect stay for 12 weeks.

33. Pharmacology of anti-D IgG
Mechanism of Action - unproven, but proposed
mechanism includes,
Masking of Rh positive fetal RBC’s before they sensitize
maternal immune system and rapid macrophage-
mediated clearance of those RBCs and/or
Down-regulation of antigen specific B cells before immune
response occurs

34. …
Mean half time - is 16-24 days irrespective of route of
administration i.e. whether IV or IM. However, peak serum
levels are reached faster with IV injection.
Efficacy- rate of alloimmunization fall from 16% to 1-2% with
single dose of routine postpartum administration of anti-D and
further reduced to 0.1 to 0.3% with addition of RAADP

35. …
Preferred site for injection
 is deltoid muscle
If gluteal region is used absorption may be
delayed and efficacy reduced by inadvertent
subcutaneous administration. (NHS guideline -
UK).

36. …
The dosage of anti-D IG after 20 weeks of
gestation is calculated from the estimated volume of
the FMH, as described below.
 One 300-μg dose is given for each 15 mL of fetal
red cells or 30 mL of fetal whole blood to be
neutralized.

37. Anti-D Administration Regimens in
RAADP
Single dose regimen - a single dose of 300mcg of anti-D Ig
at 28 weeks.

It is practiced in US and also in our setup and more convenient for the patient
than two dose regimen.
Two dose regimens – 100 to 120mcg of anti-D Ig are
administered at 28 and 34 weeks of gestation.

It is usually practiced in UK, Canada. Some meta-analysis found that two dose
regimen was more effective than a single dose regimen.

38. …
D Alloimmunization has not been completely
eliminated because of:
 Failure to administer anti-D Ig in accordance with
medical society guidelines and
Unsuspected FMH bleeding early in gestation, before
administration of RAADP.

39. …
“Whenever there is doubt whether to give anti-D
immune globulin, it should be given. If not needed, it
will not cause harm, but failure to provide it when
needed may have severe consequences”
“The rule of thumb should be to administer Rh immune
globulin when in doubt, rather than to withhold it.”
Vincent Freda,

40. Antepartum Prophylaxis for Pregnancy
Complications with FMH
Fetomaternal hemorrhage (FMH) is defined by the transfer
of fetal blood into normally separated maternal circulation
during pregnancy or delivery. In most cases of Rh
alloimmunization, FMH occurs in the antenatal period or, more
commonly at the time of delivery (90%).
Sensitization may occur after a single exposure to as little as 0.1 mL of
fetal RBC

41. …
The immune response of a Rh-negative individual to RhD-positive
red cells has been characterized into one of three groups:
Responders (60% to 70%) of individuals are responders who develop an
antibody to relatively small volumes of red cells; in these
individuals, the probability of immunization increases with
escalating volumes of cells.
A small percentage of responders can be called hyper responders in that they
will be immunized by very small quantities of red cells

42. …
Hypo-responders (10% to 20%), can be
immunized only by exposure to very large volumes
of cells.
 Non-responders (10% to 20%) of individuals who
remain appear to be non-responders

43. Causes of FMH -Sensitizing events
If occur anytime, need to be separately covered with anti-D
These include:
Pregnancy loss
Abortion, spontaneous or induced
Threatened Abortion
Ectopic pregnancy
IUFD (any trimester)

44. …
Procedures
Amniocentesis
 Chorionic villus sampling
 Fetal blood sampling
Molar pregnancy evacuation

45. …
Others
APH: AP > PP
Delivery, Vaginal or cesarean
ECV
 Abdominal trauma during pregnancy

46. Management of pregnancy loss before 20 weeks in Rh negative women
Without intervention risk of alloimmunization from spontaneous
abortion is 1.5 -2.0% and 4-5% from induced one (up-to-date
2022)
In 2022 WHO recommend against administer Anti-D Ig for
pregnancy terminations < 12 weeks (medical or surgical) but there
is no consensus among experts and organizations.
When Anti-D is to be given for <12 weeks, 50mcg (can protect
against FMH of 2.5ml) is enough as mean fetal RBC volume at 12
weeks is 1.5ml; however, giving standard 300mcg do not cause
harm

47. ...
FMH quantification is unnecessary to determine whether
more than 1 vial (300mcg) of anti-D is needed before 20
weeks, but it should generally be performed after 20 weeks.
 Some guideline does not recommend provision of anti-D
prophylaxis for threatened abortion before 10 weeks of
gestation unless there is significant clinical bleeding, not
just spotting

48. Postpartum prophylaxis
An appropriate dose of anti-D Ig should be administered to ICT
negative, Rh negative women within 72 hrs. of delivery of Rh
positive neonates.
Recognizing that 40 % of neonates born to Rh-negative women
are also Rhnegative, administration of Ig is recommended only
after the newborn is confirmed to be Rh positive.
 Cord blood typing is recommended even if prenatal cfDNA
testing suggests Rh negativity of the fetus.

49. …
If Ig is inadvertently not administered following delivery, it
should be given as soon as the omission is recognized,
because there may be some protection up to 28 days
postpartum.
If delivery occurs less than 3 weeks from the administration
of anti-D Ig used for antenatal indications such as ECV, a
repeat dose is unnecessary unless a large FMH is detected at
the time of delivery

50. …
It is estimated that in 2 to 3 per 1000 (~0.3%) pregnancies,
the volume of FMH exceeds 30 mL of whole blood.
A single dose of anti-D Ig would be insufficient in such
situations. For this reason, all Rh-negative women should
have estimation of FMH for possible additional doses after
standard dose postpartum anti-D Ig is provided.

51. FMH Estimation
ACOG recommend that, all D-negative women
should be screened at delivery, typically with a
qualitative test, followed by quantitative testing if
indicated.

52. Qualitative test
The rosette test
Identifies whether fetal D positive cells are present in the
circulation of a Dnegative woman.
 A sample of maternal blood is mixed with anti-D antibodies that
coat any D positive fetal cells present in the sample. Indicator red
cells bearing the D antigen are then added, and rosettes form
around the fetal cells as the indicator cells attach to them by the
antibodies. Thus, if rosettes are visualized, there are fetal D-
positive cells in that sample.

53. …
The test is designed to give a negative result when the
amount of FMH is <2 ml and thus will not necessitate
additional doses of anti-D Ig.
When rosette test is positive, a quantitative test with
kleihauer-Betke test or flow cytometry is recommended
to determine the percentage of fetal RBCs in maternal
blood.

54. Quantitative test
Kleihauer-Betke (KB) or Acid elation (AE) test.
Is the most commonly used quantitative test
Fetal erythrocytes contain HbF, which is more resistant to acid elution
than HbA. Following exposure to acid (the acid reagent used in KB
test is citrate), the maternal hemoglobin dissolves away and only fetal
hemoglobin remains. Therefore, after staining, the fetal erythrocytes
appearred (rose-pink) and adult erythrocytes appear as “ghosts”. The
fetal cells are then counted and expressed as a percentage of adult
cells.

55. …
There are two scenarios in which the KB may be
inaccurate:
Maternal hemoglobinopathies in which the fetal
hemoglobin level is elevated, such as β-thalassemia, and
At or near term, because the fetus may already be
producing hemoglobin A.

56. Flow cytometry,
Uses monoclonal antibodies to hemoglobin F or to the D antigen and then
measures the degree of fluorescence
Flow cytometry’s advantages over KB test:
It is an automated test that can analyze a greater number of cells than the KB
test.
 It is also unaffected by maternal levels of fetal hemoglobin and by fetal
levels of hemoglobin A.
more sensitive and accurate than the KB test,
Its disadvantage is that, it uses specialized technology not routinely
available in many hospitals.

57. The fetal blood volume involved in the FMH may be
calculated using the following formulas:
As an example, for a pregnant woman of normal size who
is normotensive and has reached full-term, the maternal
blood volume (MBV) may be estimated as 5000 ml. thus,
in a woman with a hematocrit of 35 % and whose fetus
has a hematocrit of 50 %, the calculation for a KB test
demonstrating staining of 1.7 percent of sample cells is:

58. …
A loss of this magnitude should be well tolerated
hemodynamically but would require two 300-μg
doses of anti-D immune globulin to prevent
alloimmunization.

59. Another formula recommended by American Association of Blood
Banks (AABB)
Is that the percentage of fetal blood cells by KB or flow cytometry
be multiplied by a factor of 50 (to account for an estimated
maternal blood volume of 5000 mL) to calculate the volume of the
FMH. This volume is divided by 30 to determine the number of
vials of anti-D to be administered. A decimal point is rounded up
to next higher whole number for values >=0.5. Because this
calculation includes an inaccurate estimation of the maternal blood
volume, one additional vial of anti-D is added to the calculation.

60. …
As an example, a 2.8% % KB stain is calculated to indicate
a 140 ml FMH.Dividing this number by 30 yields 4.6 vials
of anti-D which will be rounded up to 5 vials, with one
additional vial added; therefore, the blood bank would
prescribe 6 vials of anti-D (a total of 1800 μg) for this
patient.

61. …
If using an IM preparation of anti- D Ig, no more than five
doses may be given in a 24-hour period.
Should a large dose of RhIG be necessary, an alternative
method would be, to give the calculated dose using one of
the IV preparations of RhIG, two ampules—totaling 600 μg
— may be given every 8hrs

62. …
Twenty four hours after total estimated dose has been
administered, performing an ICT is recommended and a
positive ICT test or the presence of circulating fetal cells on
a rosette test demonstrates that the dose was sufficient. If
none detected, additional anti-D Ig should be administered
and the assay repeated until positive result obtained.

63. Management of ICT Positive Pregnancy -
the Alloimmunized pregnancy
Management of the alloimmunized pregnancy typically
consists of: -
Maternal antibody titer surveillance followed by ultrasound
monitoring of the fetal MCA peak systolic velocity if a critical
antibody titer is reached.
Fetal blood sampling is generally performed if the MCA peak
systolic velocity exceeds the threshold for severe anemia, with
plan for concurrent intrauterine transfusion as needed.

64. …
Of fetuses from D-alloimmunized pregnancies,
25 to 30 percent will have mild to moderate hemolytic
anemia, and
 25 percent have anemia severe enough to cause hydrops

65. …
If alloimmunization is detected and the titer is below the critical
value, the titer is generally repeated every 4 weeks for the
duration of the pregnancy (ACOG 2019a).
Maternal titers are screening tests, not diagnostic of severe
anemia, and should be discontinued once critical value is
reached; there is no benefit to repeating the titer.

66. …
Similarly, if a prior pregnancy was complicated by
alloimmunization, the current pregnancy is
considered at risk and monitoring with weekly
MCV-PSV is indicated starting from 16 to 18 weeks
of gestation regardless of titer.

67. …
Critical titer is the anti-red cell titer associated with
a risk for development of severe anemia and
hydrops fetalis.
 It’s laboratory dependent, but typically somewhere
between 1:8 and 1:32

68. Middle Cerebral Artery Doppler
Velocimetry
The anemic fetus shunts blood preferentially to the brain to
maintain adequate oxygenation. The velocity rises because of
increased cardiac output and decreased blood viscosity.
Serial measurement of the peak systolic velocity (PSV) of the
fetal middle cerebral artery (MCA) is the recommended test to
detect fetal anemia once critical titer is reached or if there is
history of affected prior pregnancy.

69. …
Serial MCA-PSV monitoring starts:
At 16-18 weeks of gestation if there is previous affected
pregnancy and
At 24 weeks of gestation in first affected pregnancy with
critical titer reached or exceeded
These are then repeated every 1 to 2 weeks

70. …
The threshold value of 1.5 multiples of the median
(MoM) for gestational age, correctly identified all
fetuses with moderate or severe anemia.
 This provided a sensitivity of 100 % (88% on
Gabbe 7th edition), with a false positive rate of
12%.

71. …
If the velocity is between 1.0 and 1.5 MoM and the slope is rising
—such that the value is approaching 1.5 MoM—MCA Doppler
surveillance is generally performed at least weekly
If the MCA peak systolic velocity exceeds 1.5 MoM or if
hydrops develops and anemia is the leading etiology, fetal blood
sampling and intrauterine transfusion should be considered.

72. …
MCA -PSV is not measured beyond 35 weeks, but
ultrasound evaluation for hydrops is performed as
needed.
 The false-positive rate of MCA-PSV increases
significantly beyond 34 weeks’gestation and stems from
the normal rise in cardiac output that develops at this
GA.

73. …
Use of amniotic fluid bilirubin assessment as an
indirect measure of the degree of fetal hemolytic is
no longer recommended and has now been replaced
by noninvasive MCA-PSV.

76. Fetal Blood Transfusion
Transfusion is generally recommended only if:
the fetal hematocrit is <30% and
GA <35 weeks
Later in gestation (>=35), the benefits of transfusion may
be outweighed by the risks of delaying delivery and
procedure related complications

77. …
Transfusion is most commonly intravascular.
However, the umbilical vein may be too narrow in
the early 2
nd
TM to readily permit needle entry, and
severe hemolysis may necessitate intraperitoneal
fetal transfusion.

78. …
If hydrops has developed, the hematocrit is usually
≤15%.
 In the setting of hydrops, peritoneal absorption may be
impaired, and some prefer to transfuse into both the fetal
peritoneal cavity and umbilical vein.

79. …
The red cells transfused are:
Creshly donated, type O negative,
cross matched and compatible to maternal blood sample,
Cytomegalovirus-negative,
Packed to a hematocrit of ~ 80 % to prevent volume
overload,
Irradiated to prevent fetal graft-versus-host reaction, and
Leukocyte-poor

80. …
Before transfusion, a paralytic agent such as
vecuronium with or without short-acting narcotic such
as fentanyl may be given to the fetus to minimize
movement.
In a non-hydropic fetus, the target hematocrit is 40 to
50 %

81. …
The volume transfused may be estimated by multiplying
the estimated fetal weight in grams by 0.02 for each 10-
percent rise in hematocrit needed.
As an example, if EFW is 1000g, fetal Hct is 20% and
our target Hct is 40%, the volume of transfusion will be
1000*0.02*2 = 40ml.

82. …
In the severely anemic fetus at 18 to 24 weeks’ gestation
do not tolerate the acute correction of their hematocrit to
normal values; a smaller volume is transfused initially, and
another transfusion may be planned for approximately 2
days later. Subsequent transfusions take place every 2 to 4
weeks, depending on the hematocrit.

83. …
The MCA-PSV threshold for severe anemia is higher
following an initial transfusion—1.70 MoM rather than
1.50 MoM. After the second procedure, the MCA
Doppler loses its validity in predicting fetal anemia.

84. …
Outcomes
The overall survival rate approximates 95 % (91%
on Gabbe 7th).
For hydropic fetuses, the neonatal survival rate is
about 80%

85. …
Complications include
Fetal death in 2 - 3.8 %
The stillbirth rate exceeds 15 % if transfusion is required before 20
weeks
Need for emergent cesarean delivery in 1 %
Infection 0.3% and
Preterm rupture of membranes in 0.3 %

86. Hemolytic Disease of the Fetus and
Newborn (HDFN)
Red cell alloimmunization results from transplacental
passage of maternal antibodies that destroy fetal red cells.
Transportation of these antibodies across the placenta during
pregnancy results in fetal and/or neonatal anemia, neonatal
hyperbilirubinemia, and ultimately hydrops fetalis.

87. …
Fetal Anemia;
Anti-D IgG is a non-agglutinating antibody that does not bind complement. This
results in
a lack of intravascular hemolysis
 sequestration and subsequent destruction of antibody-coated red
cells in the fetal liver and spleen are the mechanism of fetal anemia
Alloimmunization leads to overproduction of immature fetal and
neonatal red cells—erythroblastosis fetalis

88. …
Hydrops fetalis
Is defined by the accumulation of extracellular fluid in at least two
body compartments
Is a late finding in cases of fetal anemia –
When hydrops is present, fetal hemoglobin deficits of 7 to 10 g/dL from the
mean hemoglobin value for the corresponding gestational age can
be expected.
Its exact pathophysiology is unknown but is likely multifactorial.

89. …
Hydrops is diagnosed by identifying two or more fetal effusions
—pleural, pericardial, or ascites—or one effusion plus anasarca.
Sonographically measured skin thickness of >5 mm constitutes
edema or anasarca.
As hydrops progresses in severity, anasarca is an invariable
feature and is usually accompanied by placentomegaly and
hydramnios.

90. …
Placentomegaly is defined as placental thickness
>=4 cm in the second trimester or
 >=6 cm in the third trimester

91. …
If hydrops is found in association with red cell
alloimmunization, hydrops is termed immune (10%).
Otherwise it is nonimmune (most common type – 90%).

92. References
 Gaabbe obstetrics 7th edition
 Williams’ Obstetrics 25th and 26th edition
Medstar Obstetrics and Gynecology Second Edition
DC Dutta’s Textbook Of Obstetrics 7th edition
Ayder’s Obstetrics and Gynecology
 Up-to-date 2022

93. THANK YOU