INTRODUCTION

1.1 Background of the study 

The AB and Rhesus factor (Rh D antigen) are recognized as the major blood group antigens present in the red blood cells. In 1900, the A, B and O types were determined by Karl Landsteiner. Rhesus blood group system was the fourth system to be discovered by Landsteiner and Alexander S. Wiener in 1937.1,2 The Rhesus system is named after Rhesus monkeys which were used in the experiments that led to the discovery of the system. The presence of the Rh factor, a protein on the red cell surface, constitutes Rh+positive (Rh) person, whereas the absence of Rh factor indicates a negative (Rh) person. Dr. Philip Levine made a connection between the Rh factor and the incidence of Erythroblastosis fetalis resulting from the Rh factor. Wiener realized adverse reactions from transfusions were also resulting from the Rh factor.2,3

Determination of blood type in ABO Rh D negative pregnant women allows reasonable precautions which limit the risk to fetus. Erythoblastosis is a very serious medical condition for about 4000 babies a year. In 15% of cases of babies die before birth. Those who survive may suffer from jaundice, which leads to the deaf- muteness, speech disturbances, cerebral palsy and mental retardation.4,5 The frequency of Rh D iso-immunization in the general population continues to be a point of significance for the clinician, as this significantly contributes to morbidity and mortality in obstetric practice.6 There is a need for further studies in Rh D negative pregnant women because several factors affect the development of allo-immunization and its prognosis.7

Rh antigens are lipoprotein molecules, which are sparsely located at the erythrocyte surface. About 50 of them can be identified, which indicates the specific complexity of the Rh antigen. D antigen is the most immunogenic and therefore the most important antigen. It causes the formation of antibodies 50 times more often than the C and E antigens. Rh D negative people do not have the D antigen in the Caucasian population, 85% of people are Rh positive and 15% Rh negative. The frequency of Rh negative women is more common for Caucasian women (15%) than African American (5%) and is less common in Asian women.5,8-10

Antibodies from Rh system are almost always immune, predominantly in the IgG class, passing due to its size through the umbilical cord and cause hemolytic disease of the new born. Under Hemolytic disease of the new born (HDN) in the strict sense is considered disease whose basis is accelerated immune destruction of fetal/child erythrocytes that are bound to IgG antibodies of maternal origin. These antibodies are directed against antigens of father’s origin, which are present in the fetal/children’s erythrocytes and that the mother’s immune system recognizes them as foreign antigens. This happens if the fetal red blood cells enter mother’s circulation.10,11 Sensitization occurs during childbirth when the mother’s bloodstream penetrates certain amount of Rh positive child erythrocytes. Erythrocytes, as foreign substance to the mother, encourages her body to begin to produce Rh antibodies. Therefore, the second and other pregnancy can have complications related to maternal Rh antibodies to Rh positive fetal red blood cells.4,5,8-10 Their appearance in the circulation is also possible after amniocentesis, spontaneous or induced abortion, cardiocentesis, chorionic villus sampling, ruptured ectopic pregnancy and a blunt trauma to the abdomen.11

1.2 Statement of the problem

Rh incompatibility is a condition that develops when a pregnant woman has Rh-negative blood and the baby in her womb has Rh-positive blood. If the mother is Rh-negative, her immune system treats Rh-positive fetal cells as if they were a foreign substance. The mother's body makes antibodies against the fetal blood cells. These antibodies may cross back through the placenta into the developing baby. They destroy the baby's circulating red blood cells. Firstborn infants are often not affected unless the mother had past miscarriages or abortions. This would sensitize her immune system. This is because it takes time for the mother to develop antibodies. All children she has later who are also Rh-positive may be affected. Rh incompatibility develops only when the mother is Rh-negative and the infant is Rh-positive. This problem has become less common in places that provide good prenatal care. This is because special immune globulins called RhoGAM are routinely used.

1.3 Objective of the study

The general objective of this study is to examine the importance of Rhesus factor in marriage and child birth. The specific objectives of this study are:

1. To examine the rhesus blood group distribution among the pregnant women at University of Port Harcourt Teaching Hospital.

2. To examine the distribution of ABO blood group among the pregnant women based on rhesus blood group in the year 2014 at University of Port Harcourt Teaching Hospital.

3. To examine the distribution of ABO blood group among the pregnant women based on rhesus blood group in the year 2015 at University of Port Harcourt Teaching Hospital.

4. To examine distribution of rhesus blood group in pregnant women at University of Port Harcourt Teaching Hospital.

5. To examine the distribution of rhesus negative blood group among pregnant women in University of Port Harcourt Teaching Hospital.