Correlation between the RhD genotyping and RhD serotyping in isoimmunized pregnancies

Alloimmunisation was one of the most important causes of perinatal mortality and morbidity by the middle of the last century. The objective of the present study was to investigate the presence of the RHD gene in fetal cells (amniocytes) obtained from amniotic fluid by genotyping to compare it with the RhD serotyping. Also to correlate the presence of RhD gene with the neonatal outcome. This work was carried out at Maternity hospital and Medical Genetics center, while PCR testing was done at the Medical Research center, Faculty of Medicine, Ain Shams University in the period from 2008 to 2010. The present study included recruiting of 20 RhD negative (sensitized to the RhD antigen) pregnant mothers. The entire study group was subjected to complete general, obstetric and a detailed obstetric ultrasonographic examination. Rh typing and indirect Coomb’s test were also done. Amniocentesis was performed with a 20-gauge needle under continuous ultrasound guidance. RhD serotyping of the fetuses showed that, 14 fetuses (70%) were positive and six fetuses (30%) were negative. While using RhD gentyping 13 cases (65%) were positive and seven cases (35%) were negative (P value = 0.002). Among fetuses positive for RhD genotyping six fetuses (46%) had received postnatal treatment, while among fetuses negative for RhD genotyping, neither of them had received postnatal treatment (P value =0.032), which is statistically significant. From the present study we can conclude that, the identification of an antigen-negative fetus on the basis of the blood group genotype provides significant advantages in managing the pregnancy at risk for HDFN.Keywords: Maternal alloimmunization; Rhesus; RHD; Isoimmunization; Hydrops fetalis; Fetus; Rh negativ