What is Rh incompatibility and its implications?
Q: My blood group is A negative. I am the only member in my family with RH-ve type blood group. I am 24 years old girl soon to be married. Please tell me what are the precautions I need to take?
A:The Rh factor (rhesus factor) is a red cell surface antigen that was named after the monkeys in which it was first discovered. Rh incompatibility is a condition that occurs when a woman of Rh-negative blood type is exposed to Rh-positive blood cells and subsequently develops circulating Rh antibodies. Rh incompatibility can occur by 2 main mechanisms: it can occur when an Rh-negative mother is exposed to Rh-positive fetal red cells secondary to feto-maternal haemorrhage during the course of pregnancy from spontaneous or induced abortion, trauma, invasive obstetrical procedures, or delivery. Rh incompatibility also can occur when an Rh-negative female receives a blood transfusion that contains Rh antigens. The most common cause of Rh incompatibility is exposure to an Rh-negative mother by Rh-positive fetal blood during pregnancy or delivery, whereby red cells from the fetal circulation leak into the maternal circulation. After a significant exposure, sensitisation occurs, and maternal antibodies are produced against the foreign Rh antigen. Once produced, maternal Rh antibodies may cross freely from the placenta to the fetal circulation, where they form antigen-antibody complexes with Rh-positive fetal red cells which are eventually destroyed, resulting in a fetal haemolytic anaemia. A person is Rh blood group positive if he/she has the Rh D antigen or D antigen on the red cells of the blood and this can be as follows: Blood Type Rh positive has a Genotype of RR and Rr and a blood group of Rh negative has a genotype of rr. If a mother who is Rh negative (rr) is carrying a fetus who is Rh positive (Rr) - the fetus cannot be RR as 1 R comes from each of the 2 parents and the mother being Rh negative has no R, - the mother produces antibodies to the Rh antigens on the fetal red cells. But, if the mothers immune system is kept from seeing the fetal red cells, she will never make antibodies to the Rh antigens. This can be accomplished by giving the new mother an injection of antibodies directed against the Rh antigens on the fetal RBC. The current recommendation is that every Rh-negative non-immunized woman who presents with ante-partum bleeding or potential feto-maternal haemorrhage should receive 300 mcg of Rh IgG injection. For every 30 mL of fetal whole blood exposed to maternal circulation, 300 mcg of Rh IgG should be administered. You need not worry as blood grouping is done as a part of the ante-natal check-up followed by an ultrasound examination and standard protocols exist for handling Rh negative pregnant women.