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Rhesus factor question

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Rhesus factor question

Postby biology_06er » Sat Jun 16, 2007 11:26 pm

Hey there,

This was a multi choice question from an exam I had the other day (since found out I got it wrong) but don't know what the actual answer is...can someone please help me..

...The father is Rh- and the mother is Rh+. they have had three children without adverse problems due to the Rh factor. the mother is pregnant again. In terms of the Rh factor, the risk to the fetus within the uterus:-

is less than before
is greater than before
is the same and remains relatively moderate
never was a problem

so I chose is 'greater than before'...however i read that theres only problems with a child if the mother is Rh- and the father is Rh- cos of something having to do with antibodies thinking the baby is foreign..however in this case would the answer be 'never was a problem' because the mother won't be making antibodies or something like that...

Thanks in advance,
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Postby MichaelXY » Sun Jun 17, 2007 2:54 am

The problem arises in the following case:
The father is RH+
The mother is RH-
If the mother conceives a child who is RH+ the womans body may manufacture antibodies that attack future RH+ offspring.
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Postby Poison » Sun Jun 17, 2007 10:47 am

only a Rh- mother can have that problem. try to learn the reason of the problem and then comment. don't just memorize things. :)
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Postby khenwood » Wed Jun 27, 2007 3:21 pm

I would say "C" is your most likely answer.
Generally, there's a risk to the fetus if the father is Rh+ & the mother is Rh-. But in your test question, the status was reversed. The father was Rh- & the mother was Rh+.

So if they conceive another child, it will "probably" be ok.

"D" wouldn't be correct because there's still a slim chance the fetus would be affected.
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Postby Revenged » Sun Jul 01, 2007 1:06 pm

khenwood wrote:I would say "C" is your most likely answer.
Generally, there's a risk to the fetus if the father is Rh+ & the mother is Rh-. But in your test question, the status was reversed. The father was Rh- & the mother was Rh+.

So if they conceive another child, it will "probably" be ok.

"D" wouldn't be correct because there's still a slim chance the fetus would be affected.


no, the answer is D... C states that is there is a moderate risk to the foetus which is not true... as a mother who is Rhesus positive will never develop anti-Rhesus antibodies... thus in terms of the Rh factor, the risk to the foetus within the uterus is never a problem...
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Postby Revenged » Sun Jul 01, 2007 1:20 pm

MichaelXY wrote:The problem arises in the following case:
The father is RH+
The mother is RH-
If the mother conceives a child who is RH+ the womans body may manufacture antibodies that attack future RH+ offspring.


true but you missed out an important point as only the second Rhesus positive child that the mother carries will have haemolytic disease of the newborn... the first Rhesus positive child to a Rhesus negative mother is born without any problems...

this is because the blood in the placenta is separate and will only mix during birth of the first child... and so the anti-Rhesus antibodies develop only once the first child is born... thus any subsequent Rhesus positive children the mother will have will suffer haemolytic disease of the newborn since the anti-Rhesus antibodies will pass through the placenta and will affect the foetus...

but only some antibodies will do this... for example, in a type A mother giving birth to a type B foetus - the anti-B antibodies present within the maternal plasma cannot pass through the placenta (unless something is wrong)...

http://en.wikipedia.org/wiki/Hemolytic_ ... he_newborn
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