ABSTRACT
Objective:To investigate the RHD genotypes of RhD-negative pregnant women and explore the optimum strategy for fetal RHD screening among this population in the region. Methods:This prospective study recruited 33 cases of RhD-negative singleton pregnancies at ≥12 weeks of gestation in Nanjing Drum Tower Hospital from March to November 2021. On the basis of RHD genotyping, quantitative real-time polymerase chain reaction (PCR) was used to amplify the exons 5 and 10 of RHD gene in the circulating cell-free DNA of RhD-negative pregnant women harboring whole RHD gene deletion and RHD-CE(2-9)- D. High-throughput sequencing was performed to detect chr1:25648453 locus from circulating cell-free DNA in plasma of RhD-negative pregnant women harboring RHD 1227A mutation to screen the fetal RhD blood group. Neonatal umbilical cord blood samples were collected for verifying fetal RHD genotyping. Descriptive statistical analysis was used. Results:Whole RHD gene deletion homozygous genotype ( n=20, 60.6%), RHD-CE(2-9) -D/whole RHD gene deletion heterozygous genotype ( n=5, 21.2%), RHD 1227A/whole RHD gene deletion heterozygous genotype ( n=7, 15.2%) and RHD 711delC/whole RHD gene deletion heterozygous genotype ( n=1) were identified in the 33 RhD-negative pregnant women. In the 25 cases with whole RHD gene deletion homozygous genotype or RHD-CE(2-9)- D/whole RHD gene deletion heterozygous genotype, 22 fetuses were RhD-positive and three were RhD-negative based on prenatal screening, which were confirmed by the neonatal serological test results after birth. In the seven cases carrying RHD 1227A/whole RHD gene deletion heterozygous genotype, all fetuses were RhD-positive, which were consistent with the results of serological detection after delivery. The case harboring RHD 711delC/whole RHD gene deletion heterozygous genotype did not receive fetal RHD screening. Conclusions:This study suggests that whole RHD gene deletion homozygous genotype is the most common allele in RhD-negative population in this area, followed by RHD 1227A/whole RHD gene deletion heterozygous genotype and RHD- CE(2-9)- D/whole RHD gene deletion heterozygous genotype. For women with whole RHD gene deletion homozygous genotype, RHD- CE(2-9)- D, or RHD 1227A mutation, fetal RHD screening with quantitative real-time PCR and high-throughput sequencing are important for the management of RhD-negative pregnant women.