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Chapter-13 Rh Negative Pregnancy

BOOK TITLE: Management of High-Risk Pregnancy—A Practical Approach

Author
1. Nigam Aruna
ISBN
9789380704739
DOI
10.5005/jp/books/11228_13
Edition
1/e
Publishing Year
2010
Pages
18
Author Affiliations
1. Lady Hardinge Medical College and SSK Hospital, New Delhi, India, Hamdard Institute of Medical Sciences and Research, New Delhi, India, Hamdard Institute of Medical, Sciences and Research, Jamia Hamdard, New Delhi, India
Chapter keywords

Abstract

Maternal alloimmunization, also known as isoimmunization, occurs when a woman’s immune system is sensitized to foreign erythrocyte surface antigens, stimulating the production of immunoglobulin G (IgG) antibodies. The most common routes of maternal sensitization are via blood transfusion or fetomaternal hemorrhage (FMH). Only IgG class antibodies cross the placenta and bind to the fetal red blood cells. Anti-D alloimmunization remains the most important cause of fetal hemolytic disease. All sequelae of the disease (hydrops fetalis, reflecting cardiac and hematologic events) are secondary to hemolysis or severe anemia and are potentially preventable. The blood type and Rh group should be done in all the pregnant females at their first prenatal visit and an antibody screening is also recommended using a combination of indirect and direct methods. Anti-D immunoglobulin effectively prevents maternal alloimmunization. It should be given after amniocentesis, at 28 weeks of gestation, episodes of vaginal bleeding and after delivery of Rh positive child. The dose for the prevention of Rh alloimmunization in first trimester is 50 mcg and thereafter 300 mcg after 20 weeks of gestation or more according to amount of fetomaternal hemorrhage. The management of the pregnant alloimmunized woman utilizes both invasive and noninvasive methods of maternal/fetal evaluation. In these pregnancies indirect Coombs tests are performed at monthly intervals after 18 weeks of gestation until the critical titer for laboratory is exceeded .MCA-PSV is performed weekly once the critical titer is exceeded. Amniotic fluid bilirubin and MCA-PSV can be used together in the diagnosis of fetal anemia. The treatment of the significant fetal anemia (hematocrit <30%) prior to 34 weeks of gestation is intrauterine transfusion. Delivery may be safely delayed until 37-38 weeks of gestation if intravascular transfusion is done.

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