Rh incompatibility

Introduction: A blood type (also called a blood group) is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of RBC.
The Rh blood group system is the second most important blood group system out of the 30 human blood group system after the ABO blood groups.

If you are Rh-positive, it means you have rhesus antigen on your red blood cells.
Rh-negative means you don't have rhesus antigen.
A Rh-negative person can develop antibodies to the Rh-positive antigen.

Disclaimer: The cartoon comics, humor and analogies are pedagogical tool to promote learning. It is not intended to mock or downplay the seriousness of these conditions.

Analogy: Think of Rh-positive antigen as a target and antibodies as arrows.

What is Rh incompatibility?
Rh incompatibility occurs when an Rh-negative person is exposed to Rh-positive red blood cells (RBCs).
His immune system will destroy the Rh-positive cells by making antibodies (Anti-D antibodies or the arrows).
This person is now sensitized.
(Simply put, a sensitized person has arrows against the target or can rapidly make arrows from his memory if exposed to the same target again.)
Rh antigen and antibody
Rh incompatibility in first pregnancy:
Rh incompatibility occurs when an Rh-negative pregnant mother is exposed to Rh-positive fetal red blood cells (RBCs).
(Mummy red blood cells don't have the target and baby cells have the target!)

When does that happen?
Usually, there is no mixing of fetal and maternal blood.
But it can occur secondary to fetomaternal hemorrhage during the course of pregnancy from spontaneous or induced abortion, trauma, invasive obstetric procedures, or even normal delivery!
(Kid's RBCs are mixed with mom's un-targeted RBCs.)

Rh-negative mother becomes alloimmunized to the Rh antigen present on fetal red blood cells during the first Rh-incompatible pregnancy.
(The mother's immune system notices the cells with the target!)

The first pregnancy is rarely affected because the number of Rh antibodies produced by the mother during primary immunization is low and the antibodies are usually IgM in nature. IgM can’t cross placental barrier.
(The mother's white blood cells make arrows, but they are little in number.
They are also too big to pass through the placenta.
[Think of the placenta as a wall, or a barrier, with really tiny windows, protecting the fetus].
This is why, the child's targeted RBCs are safe and sound in the first pregnancy.)

First Rh incompatible pregnancy

Rh incompatibility in subsequent pregnancy:
When the mother is exposed to Rh-positive fetal RBCs during a subsequent Rh-incompatible pregnancy, the mother mounts a secondary immune response to the fetus’ RBCs.
(Mother's white blood cells rapidly recognizes the targeted RBCs and bulls eye!)

A large number of IgG-class Rh antibodies are produced. The IgG antibodies cross the placenta and make fetal red cells susceptible to destruction.
(This time, the mother's white blood cells produces many smaller arrows that can go through the small windows in the wall [placenta].)

Note: If the mother is sensitized to the Rh antigen prior to the first pregnancy, say due to some blood transfusion or environmental exposure, the first fetus will be affected.

Rh incompatibility during second exposure to Rh antigen
The fetal RBCs are then destroyed by the fetal immune system. Anemia develops in the fetus with a concomitant increase in unconjugated bilirubin. The anemia and unconjugated bilirubin levels can lead to a number of conditions like jaundice, kernicterus, hepatomegaly, splenomegaly and worst case scenario, eventual death.

The good news is, sensitization is preventable and even after first exposure, subsequent child can be protected from mom's antibodies by administration of Rh IgG =)

Wanna reblog? Here's the link to the tumblr post!

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