Further to the last post - fetal Rh testing
The article published on the BMJ is:
Effect of high throughput RHD typing of fetal DNA in maternal plasma on use of anti-RhD immunoglobulin in RhD negative pregnant women: prospective feasibility study
The article published on the BMJ is basically saying that a sample of the mother’s blood was taken at about 28wks and fetal cells looked at in the blood. Yes, a very small amount of cells do cross into the maternal blood so in fact, if you have boys, you have male cells circulating in your blood. If cells other than red blood cells are found, they can be analysed with highly sensitive analysis that looks at the DNA.
The study was of 1869 samples of cord blood, which here in SA is always taken when the mother is Rh-. There was a 95.7% agreement between the genetopying and the blood sample testing, but 3.4% of the tests were unobtainable or inconclusive. There was a small number (0.8%) of genotype tests that showed a positive (baby was Rh+) when in fact they were Rh- and in 0.2% a false negative (baby was Rh-) when in fact the bab was Rh+. If treatment was based on these results, only 2% of women would have received treatment unnecessarily, rather than 38% without.
Here in SA, prophilactic treatment is given at 28wks and 34wks, and then based on the Rh status of the babe, after birth as well.
And possibly, when this kind of DNA testing is improved, it will take the place of amniocentesis!
