Unlike the ABO blood groups, there are no pre-formed antibodies here. This means that both Rh+ and Rh- people lack Anti-D antibodies. An exception to this is Rh- people who have received blood from Rh+ people. The Rh- person will create Anti-D antibodies against the Rh+ blood cells. If an Rh- person donates blood to an Rh+ person, no antibodies will be formed because there are no D antigens to initiate the formation of anti-bodies( remember that Rh+ people have the D antigen, Rh- people lack it)<\/strong>.<\/p>\n\n\n\n In summary, Rh+ people lack Anti-D antibodies(because they have D antigen, it would be lethal for them so it makes no sense for them to have it) and Rh- people also lack Anti-D antibodies except for those who have previously received blood from an Rh+ person.<\/strong><\/p>\n\n\n<\/span>\n As discussed previously, all Rh- people lack Anti-D antibodies except for those who have received blood from an Rh+ person before.<\/p>\n\n\n\n This same rule applies in pregnancy because during childbirth, there is some mixing of blood between the mother and the fetus(not during pregnancy, just childbirth) and this mixing, although not a blood transfusion, will still lead to the formation of Anti-D antibodies i.e if an Rh- mother is pregnant with an Rh+ child, during childbirth, the mixing of blood will cause the Rh- mother to develop Anti-D antibodies against the Rh+ blood of the fetus. As discussed previously, this mixing will not form Anti-D antibodies in the fetus as the maternal Rh- blood lacks antigens(antigens are needed for the formation of antibodies)<\/p>\n\n\n\n To further explain this, I will make a cross between a homozygous dominant father and a homozygous recessive mother.<\/p>\n\n\n\n Parental phenotypes: Rh+ \u00d7 Rh-<\/p>\n\n\n\n Parental genotypes: DD\u00d7dd<\/p>\n\n\n\n Parental gametes: \u24b9\u24b9\u00d7 \u24d3\u24d3<\/p>\n\n\n\n F1 genotype: Dd<\/p>\n\n\n\n F1 phenotype: All Rh+<\/p>\n\n\n\n During the first pregnancy, there is no problem(assuming the Rh- mother has not received a blood transfusion before). During birth, the mixing of blood between the mother and the fetus introduces Rh+ cells into the mother’s blood and stimulates the production of Anti-D antibodies. The Rh+ cells are then eliminated from the mother’s blood but the Anti-D antibodies remain.<\/p>\n\n\n\n During the second pregnancy(as seen in the cross above, the second child is also Rh+), the Anti-D antibodies in the mother will travel through the placenta and attack the red blood cells of the fetus(remember that the Rh+ fetus’ cells have D antigen on their surface). This antigen-antibody reaction leads to agglutination<\/strong>. It is observed as hemolytic disease of the newborn<\/strong>, with the most severe complication being hydrops details <\/strong>— a severe and generalized accumulation of fluid in body tissues and cavities in the newborn.<\/p>\n\n\n\n To prevent this from happening, Rh- mothers with Rh+ husbands (and Rh- mothers who have previously received Rh+ blood) should be given an injection at 28 weeks of the first pregnancy. This will prevent the Anti-D antibodies from being formed in the first place and poses no risks for subsequent births.<\/p>\n\n\n\n This event does not affect the ABO blood system i.e if an A+ mother(with Anti-B antibodies in her plasma) is pregnant with a B+ fetus(with B antigen on the surface of the red blood cells), it will not cause any problems. This is because the antibodies in the ABO system are IgM<\/strong>, a pentamer that is too big to cross the placenta but antibodies in the Rhesus system are IgG<\/strong>, small monomers that can easily cross the placenta.<\/p>\n<\/span>Role of Rhesus factor in pregnancy<\/h4>\n<\/span>\n\n\n
<\/td> \u24b9<\/td> \u24b9<\/td><\/tr> \u24d3<\/td> Dd<\/td> Dd<\/td><\/tr> \u24d3<\/td> Dd<\/td> Dd<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n