[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Immunology](https://durgical.com/en/immunology/) › [Hypersensitivity](https://durgical.com/en/immunology/#a-hypersensitivity) › ABO and Rh blood groups, hemolytic disease of the newborn [Immunology](https://durgical.com/en/immunology/) · [Hypersensitivity](https://durgical.com/en/immunology/#a-hypersensitivity) # ABO and Rh blood groups, hemolytic disease of the newborn - Topic A person's blood group is set by sugars (A, B) and a protein (Rh) on red cells. A mismatch in a transfusion or between mother and baby can destroy red cells. Updated 2026-11-01 **See it in 3D:** [Spleen](https://durgical.com/en/anatomy/spleen/) ## Key points - Group O red cells = universal donor; group AB = universal red-cell recipient; AB plasma = universal plasma. - Anti-A and anti-B are natural antibodies (no prior transfusion needed); anti-D needs prior exposure. - Rh disease: Rh-negative mother, Rh-positive baby, usually affects the second and later pregnancies. - Rh immunoglobulin prevents sensitization; it is useless once the mother already has anti-D. - ABO hemolytic disease: group O mother, group A or B baby, can affect the first pregnancy, usually mild. ## What it is The ABO system is defined by A and B antigens on red cells; from early infancy people make antibodies against whichever of A and B they lack, without ever being transfused. The Rh (D) antigen is either present (Rh-positive) or absent (Rh-negative), and anti-D appears only after exposure through transfusion or pregnancy. These rules decide which blood is safe to give. They also explain hemolytic disease of the fetus and newborn, when maternal IgG crosses the placenta and destroys the baby's red cells. ## Key facts - Plasma follows the opposite rule: AB plasma has no anti-A or anti-B, so it can go to anyone; group O plasma only to group O. - Rh-negative patients, above all girls and women who may become pregnant, receive Rh-negative red cells to avoid making anti-D. - Anti-A and anti-B are mainly IgM, which does not cross the placenta; group O mothers can also make IgG anti-A and anti-B. - Group O is the most common group worldwide and AB the rarest. ## Step by step - An Rh-negative mother carries an Rh-positive baby (the Rh-positive trait comes from the father). - At delivery, a miscarriage, an abortion, an invasive test or abdominal trauma, fetal red cells enter her blood. - She makes anti-D; the first baby is usually spared because the response comes late and starts as IgM. - In the next Rh-positive pregnancy, memory IgG anti-D crosses the placenta and coats the fetal red cells. - The fetal spleen destroys them: anemia, jaundice and, in severe cases, hydrops fetalis or kernicterus. ## ABO red-cell compatibility | Blood group | Antigen on red cells | Antibodies in plasma | Can receive red cells from | Can give red cells to | | --- | --- | --- | --- | --- | | O | None (H only) | Anti-A and anti-B | O only | O, A, B and AB (universal red-cell donor) | | A | A | Anti-B | A and O | A and AB | | B | B | Anti-A | B and O | B and AB | | AB | A and B | None | AB, A, B and O (universal red-cell recipient) | AB only | ## Clinical notes - Rh immunoglobulin (anti-D) given to an unsensitized Rh-negative mother clears fetal Rh-positive cells before her immune system can respond. It is given during pregnancy, after the birth of an Rh-positive baby and after any event that can mix fetal and maternal blood. - It only works before sensitization; once the mother has made her own anti-D, it no longer helps. - ABO hemolytic disease is usually seen in group A or B babies of group O mothers, can occur in the first pregnancy and is generally milder than Rh disease. - Indirect Coombs on the mother screens for anti-D and other antibodies; direct Coombs on the baby shows antibody on its red cells. ## Memory aid Red cells: O gives to all, AB takes from all. Plasma flips the rule: AB gives to all. ## Test yourself Think of the answer, then tap the question to see it. ## Why can a group O person receive only group O red cells? Group O plasma contains both anti-A and anti-B, which would destroy red cells carrying A or B antigens. ## Why is the first Rh-positive baby of an Rh-negative mother usually unaffected? She is sensitized mainly at delivery, and her first response is slow and mostly IgM, which does not cross the placenta. Later pregnancies meet ready IgG anti-D. ## How does Rh immunoglobulin prevent hemolytic disease in later pregnancies? The passive anti-D removes fetal Rh-positive red cells from the mother's blood before her own B cells can respond, so she never makes memory anti-D. ## Which plasma group can be given to a patient of any ABO group? Group AB plasma, because it contains neither anti-A nor anti-B. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/immunology/abo-and-rh-blood-groups-hemolytic-disease-of-the-newborn/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Spleen](https://durgical.com/en/anatomy/spleen/) ## Related - [Transfusion reactions](https://durgical.com/en/immunology/transfusion-reactions/) - [Type II hypersensitivity (antibody against cells)](https://durgical.com/en/immunology/type-ii-hypersensitivity/) - [Direct and indirect Coombs test](https://durgical.com/en/immunology/direct-and-indirect-coombs-test/) - [Passive immunization: immunoglobulins and antitoxins](https://durgical.com/en/immunology/passive-immunization-immunoglobulins-and-antitoxins/) - [Antibody structure and isotypes (IgG, IgA, IgM, IgE, IgD)](https://durgical.com/en/immunology/antibody-structure-and-isotypes/) - [Neonatal immunity: maternal IgG and breast-milk IgA](https://durgical.com/en/immunology/neonatal-immunity-maternal-igg-and-breast-milk-iga/) ## Related conditions - [Neonatal jaundice](https://durgical.com/en/conditions/neonatal-jaundice/) [← All of immunology](https://durgical.com/en/immunology/) Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given. Sources: [ABO Blood Group System](https://www.ncbi.nlm.nih.gov/books/NBK580518/) (StatPearls Publishing (NCBI Bookshelf), 2025); [Rh incompatibility: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001600.htm) (MedlinePlus, U.S. National Library of Medicine, 2025); [21.7 Transplantation and Cancer Immunology](https://openstax.org/books/anatomy-and-physiology-2e/pages/21-7-transplantation-and-cancer-immunology) (OpenStax, Rice University (Anatomy and Physiology 2e), 2022). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/immunology/abo-and-rh-blood-groups-hemolytic-disease-of-the-newborn/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/abo-and-rh-blood-groups-hemolytic-disease-of-the-newborn/