1	One Step Further Hemolytic Disease of the Newborn OSF - 13 Page 266
2	HDN - 2 Mechanism of disease: ewoman has been exposed to red blood cell antigens which are not found on her own red blood cells and her immune system has responded by producing antigen-specific antibodies ethese maternal antigen-specific IgG antibodies cross the placental barrier and attach to fetal red cells having the antigen on them efetal red cells are then lyzed and resulting bilirubin is handled by maternal liver eonce the baby is delivered the baby=s liver must handle the bilirubin emost frequent antigen-antibodies involved in HDN are: A antigen/anti-A antibodies B antigen/anti-B antibodies D antigen/anti-D antibodies other Rh antigens/anti-Rh antibodies ABO HDN Rh HDN
3	HDN - 3 Mechanisms of Disease cont=d: ein the case of ABO HDN: the 1st child may be affected since mom already has the antibodies in her circulatory system i.e. mom is O type and baby is A or B type ein the case of Rh HDN: usually the 1st child is not affected since it is the Rh+ red cells of the fetus that get into moms circulation during delivery and sensitize the mom.
4	HDN - 4 Immunologic testing: ePrenatal evaluation: indirect antiglobulin test (antibody screen) ‡if IgG class antibodies are detected the mother=s antibody titer is monitored during pregnancy ‡increasing titer indicates HDN ‡steady titer indicates antigen comatibility between fetus and mom=s red cells indirect antiglobulin test (antibody screen) direct antiglobulin test (DAT) blood typing ‡performed on mom after delivery ‡if positive the antibody is identified eNeonatal evaluation:
5	HDN - 5 Immunologic testing: continued eNeonatal evaluation: direct antiglobulin test (DAT) blood typing ‡performed on cord blood ‡detects antibodies attached to fetal red cells ‡if positive antibodies are eluted off the red cells and identified and NBIL* is ordered *NBIL = neonatal bilirubin test measures unconjugated bilirubin ‡blood type of newborn is performed using forward typing only (no anti-A or anti-B formed yet to perform reverse typing) ‡if mom is O type and newborn is A, B, or AB it alerts the physician to possible ABO HDN and bilirubin can be monitored
6	HDN - 6 Preventive measures: eRhoGAM women who are Rh-D negative and give birth to a Rh-D positive child are given anti-D (RhoGAM or Rh immune globulin) injection within 72 hours of delivery ‡the anti-D will attach to any Rh-D positive fetal cells in mom=s circulation and these cells will be destroyed before mom=s immune system is sensitized Women who are Rh-D negative and are pregnant may be given RhoGAM during 28th week of pregnancy to have anti-D in mom=s circulation should any Rh-D positive red cells from developing fetus make it into mom=s circulatory system during pregnancy
7	End of HDN