Presentation on theme: "8th Edition APGO Objectives for Medical Students"— Presentation transcript:
18th Edition APGO Objectives for Medical Students Isoimmunization
2RationaleThe problem of fetal hemolysis from maternal D isoimmunization has decreased in the past few decades. Awareness of the red cell antigen-antibody system is important to help further reduce the morbidity and mortality from isoimmunization.
3Objectives The student will demonstrate knowledge of the following: Red blood cell antigensUse of immunoglobulin prophylaxis during pregnancyClinical circumstances under which isoimmunization is likely to occurMethods used to determine maternal isoimmunization and severity of fetal involvement
4Red blood cell antigens Three genetic loci - C, D, EPossible alleles - Cc, Dd, Eed = absence of discernible allelic productMinor antigens not as frequent as anti-D
15Management of Rh negative mother Maternal antibody titer negative - do serial antibodiesIf titer low - little risk of anemiaIf > 1:16 - perform amniocentesis and/or Doppler assessment∆OD450 plot on Liley curveZone I - Rh negative or fetus mildly affectedZone II - moderately affectedZone III - high risk for IUFD
16Fetal management - Rh negative, Ab positive mother Serial sonogramsEarly signsThickened placentaLiver spanIncreased umbilical vein diameterIncreased blood velocities in UV, aorta and middle cerebral arterySevere disease - scan every week if hydropic changes. If hydropic changes, consider fetal transfusion.
17Fetal management - Rh negative, Ab positive mother Serial amniocentesis∆OD450 measurementLiley curveLow - Zone II and lower - deliver at fetal maturityHigh - Zone II and higher - deliver before maturity
18Fetal management - Rh negative, Ab positive mother Fetal antigen statusDNA analysisPUBS at ~20 wk.
19Transfusion therapy Intraperitoneal First done in 1963 Instill blood through needle or epidural catheterVolume to transfuse = (G.A.-20) x 10mlGenerally, repeat in ~ 10 days, then every 4 wk.Risk of death about 4% per procedureNot effective in hydropic fetusSome advocate combined approach (IPT and IVT)
20Transfusion therapy Intravascular Goal is to have post-transfusion Hct 40-45%Can infuse about 10 ml/minEstimate requirement based on EFW and pre-transfusion HctRepeat in 1 wk., then about every 3 wk.Hct falls about 1%/dayGoal: keep Hct > 25%Smaller volumes, therefore more procedures compared to IPTFetal loss about 1.5% per procedure
21References(*Texts targeted to medical students and general womenﾕs health care providers)*Beckmann CRB, Ling FW, Abnormal obstetrics in Obstetrics and Gynecology, 4th ed, 2002; chapter 11:*O’Shaugnessy R, Kennedy M. Isoimmunization in Ling FW, Duff P. Obstetrics & Gynecology Principles for Practice, 2001:chapter 10:Cunningham FG, Gant NR, Leveno KJ, Gilstrap LC, Hauth JC, Wenstrom KD. Diseases and injuries of the fetus and newborn inWilliams Obstetrics 21st ed., 2001: chapter 39: Jackson M, Branch DW. Alloimmunization in pregnancy in Gabbe SG. Obstetrics Normal and Problem Pregnancies 4th ed., 2002:chapter 26:
23ObjectivesAt the conclusion of this exercise, the student will be able to demonstrate knowledge of the following:Red Cell AntigensUse of immunoglobulin prophylaxis during pregnancyClinical situations under which D isoimmunization are likely to occurManagement of the at-risk pregnancy
24Patient PresentationA 32-year-old woman, P1101, and her new husband present for prenatal care at 20 weeks’ gestation. Her past obstetric history is significant for a first child delivered at term following an abruption. Her second child died of complications of prematurity following in utero transfusions for Rh isoimmunization. Her initial prenatal labs this pregnancy indicate her blood type as A negative and an antibody screen positive for anti-D with a titer of 1:64. You discuss any additional evaluation needed, her risks in this pregnancy, and the plan of management with her and her husband.
25Teaching PointsWhat is Rh isoimmunization and what are the red cell antigens involved?What are the risk factors for Rh isoimmunization?What is the mechanism for RhoGAM prophylaxis against Rh disease?What is the dose of RhoGAM?What is the recommended schedule for RhoGAM administration?
26Teaching PointsCould this patient’s Rh isoimmunization have been prevented?Is there any further blood work that should be obtained before you counsel this patient on her risks in this pregnancy?Discuss the management of the Rh-sensitized mother in an at-risk pregnancy.What are some ultrasound findings that may suggest Rh disease?