Rhesus alloimmunization in pregnancy. A tertiary care center experience in the Western region of Saudi Arabia.

OBJECTIVE To determine the distribution of ABO blood group and rhesus (RH) factor among pregnant women, to estimate the prevalence of Rh alloimmunization, and report the perinatal outcome of all cases of Rh alloimmunization at King Abdul-Aziz University Hospital (KAUH). METHODS This is a retrospective study of pregnant women attending the antenatal clinics in KAUH, Jeddah, Saudi Arabia between January 2004 and December 2009. Records of patient diagnosed as Rh negative blood group were reviewed for the presence of antibodies, antibodies titer, and progress in the level of antibodies. Maternal and neonatal outcomes were reported. RESULTS Twenty-four thousand and five pregnant women were included in this study. The most common blood group was O followed by A, B and AB positive. Rhesus negativity blood group was reported in 7.5%. Four hundred and twenty-four cases were reported as Rh antibody positive with a prevalence of alloimmunization of 1.8% in the studied population, and 23.6% among Rh negative women. The perinatal mortality rate was 250 per 1000 in alloimmunized women compared to 17 per 1000 in the study population. CONCLUSION Blood group O positive is the most prevalent blood group among pregnant women attending our antenatal clinics and the prevalence of Rh negativity was 7.5%. The prevalence of Rh alloimmunization in the present study was 10-folds higher than that reported in the developed countries. Rhesus alloimmunization represent an avoidable direct cause for perinatal morbidity and mortality in our population.