I took this from midwifery is catching.
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, 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.
So I now know how they do the test. The treatment will never only be based on this because of the possibilty of a false result, and even though it is small no doctor would realistically want to take the chance. God they won’t even take a chance on a woman going into spontaneous labour.
In addition they couldn’t get a result from 3.4% of the tests. Can you imagine the freak out over that. GP’s in SA are already unhappy about carrying the responsibility of first trimester screening as it’s not offered in the hospital system. I can just see the stress when they have to do a test, interpret the result and then maybe it won’t be readable or it could be a false negative. Oh happy days.
PLEASE DON’T FORGET ABOUT CHOICE
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Ok so I am RHnegative.. I am having my third baby.. The first two are both A- like me, Dad is 0+. I am concerned as I know Anti D is a blood product and that bothers me.. I actually had trouble getting it for 28weeks. Had the hospital tell me I had to come up with 2kids (3yr & 1yr) on a completely different day just to get a 2min injection. I told them I couldn't do that and I received all kinds of attitude.
Then they did the bloods at my next visit at about 3pm in the afternoon and promptly told me that I need to have it as it will make it hard to have future children (a scar tactic I think that should not be used on someone that has had two miscarriages) and I could have the Anti D that day but I would have to wait till they got test results back. God only knows how long that would take so again I said that I couldn't do that (Because of 2 kids) Didn't want to be leaving the hospital at 6pm or later for a lousy injection.
Sorry went on a tangent.. My problem is this I don't seem to be able to find out what my chances are of having a positive blood baby when I have already had 2 Children with Identical blood types as me.. Could you help me with this..
The chance is the same every time.