FetalRHDgenotyping in maternal serum during the first trimester of pregnancy

Abstract

Summary. Fetal RHD genotype determination is useful in the management of sensitized RhD-negative pregnant women. It can be ascertained early during pregnancy by chorionic villus sampling (CVS) or amniocentesis. However, these procedures are invasive, resulting both in an increased risk of fetal loss and in an increased severity of immunization due to fetomaternal haemorrhage. A reliable determination of RHD genotype by fetal DNA analysis in maternal serum during the first trimester of pregnancy is reported in this study. One hundred and six sera from RhDnegative pregnant women were obtained during the first trimester of pregnancy. These sera were tested for the presence of RHD gene using a new real-time polymerase chain reaction assay and the results compared with those obtained later in pregnancy on amniotic fluid cells and by RHD serology of the new-born. All sera from women carrying a RhD-positive fetus (n ¼ 62) gave positive results for RHD gene detection and sera from women carrying a RhDnegative fetus (n ¼ 40) were negative. The high level of accuracy of fetal RHD genotyping obtained in this study could enable this technique to be offered on a routine basis for the management of RhD-negative patients during the first trimester of pregnancy.

High throughput non-invasive determination of foetal Rhesus D status using automated extraction of cell-free foetal DNA in maternal plasma and mass spectrometry

“…Non-invasive prenatal RHD analysis is currently most frequently performed using real-time PCR, either in conjunction with manual or automated procedures for the extraction of cell-free DNA from the maternal plasma/ serum samples [4,9,13,15,16,19]. In this study, we analysed the foetal RHD status by mass spectrometry, in combination with automated system for the extraction of cell-free DNA from maternal plasma.…”

Noninvasive prenatal diagnosis of fetal blood group phenotypes: current practice and future prospects

“…Our practice is to process the maternal blood within 48 h of venepuncture, but from experiments in our laboratory any time up to 7 days should be acceptable (Finning K, unpublished observations). Spiking of the plasma with mouse DNA, maize DNA, or Escherichia coli plasmid, followed by specific detection, provides a control for sensitivity of the test (Costa et al, 2002;Legler et al, 2002;Rouillac-Le Sciellour et al, 2007 …”

Non-invasive fetal RHD genotyping tests: A systematic review of the quality of reporting of diagnostic accuracy in published studies

“…A test failure rate, which is derived from the number of excluded samples due to inconclusive results, lack of material or maternal variant genes, was reported in only 12 studies [4][5][6][13][14][15][16]25,[29][30][31]35]. Out of these, only one group of authors considered the failure rate in their analysis of test accuracy [31] and one mentioned the revised overall success rate only in their comments [15].…”

“…Table 2 clearly indicates that a number of researchers concentrated on samples from at risk pregnancies (e.g. Down syndrome), including women who may not resemble the general RhD-negative pregnant population [5,8,9,15,[23][24][25][26]. Since recruitment was carried out selectively, test accuracy reported in such studies might be an overestimate because certain fetal conditions …”

“…Following the first papers, research interest in this form of non-invasive prenatal diagnosis (NIPD) has become global. Publications in Europe, America and Australia aim to improve the management of pregnancies of women who are rhesus negative [2,[4][5][6][7][8][9]. In white Caucasian populations about 10% of all pregnancies involve an RhD-negative mother and an RhD-positive fetus, potentially placing the mother at risk of sensitisation and future babies at risk of haemolytic disease of the fetus and newborn (HDFN).…”