Testing brother's blood for infertility?

The brother of my fiance is infertile and he asked my fiance to be the sperm donor. He din't accept. 

Now I saw in my fiance's arm the sign that he had given blood. I asked him what's that about. He said that the doctor of his brother had asked for the blood of family members to test if there's something genetic in the infertility. 

Is this even possible? What does the blood of the brother have to do with infertility?

The BIG question is: is my fiance donating the sperm for his brother?

Update:

I read that sperm donors have to do urine and blood tests:

https://www.mayoclinic.org/tests-procedures/sperm-...

8 Answers

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  • John P
    Lv 7
    1 month ago

    Sperm does not come from the arms!!!   Whether or not your fiancé has donated sperm there will be no trace of that action or lack of it on his arms or in his blood.

    Did your school really tell you nothing about sex and pregnancy and heredity and so on?

  • 1 month ago

    why don't you just ask your fiance? If you got engaged, you must be at a level of your relationship where you can talk about stuff like this, otherwise its all a big sham

  • 2 months ago

    There are 2 types of infertility in which men get genetic testing. 

    The first is when they have a condition called non-obstructive azoospermia (NOA). Men with NOA have severe sperm production problems and should have 2 blood tests: 1) micro-Y deletion and 2) chromosomal analysis. Men with NOA due to a genetic cause (it can also be caused by history of radiation treatment or chemotherapy) are understood to have the mutation arisen spontaneously in them. By definition the genetic mutation cannot be inherited. The reason for this is that if a man's father had the same NOA genetic mutation, then he would not have children in the first place so the mutation would not be passed on. For that reason, there is no particular reason to check the brother of a man who has a genetic issue causing the NOA type of infertility.There is another type of infertility called obstructive azoospermia (OA). Sometimes these men are carriers of a cystic fibrosis gene. It's possible that they're a carrier of this gene even if they don't express cystic fibrosis or have anyone in their family that's known to have cystic fibrosis. Having the CF gene, however, can cause blockage (or obstruction) in the pathway of sperm. The genetic test for these men is a blood test called CFTR.  So, if a man is determined to be a CF carrier and this is causing him to have obstructive azoospermia, then any of his brothers also have a chance of having the same condition and this could be determined by a blood test. 

  • Anonymous
    2 months ago

    Personally, I feel like taking a mouth swab or saliva sample would yield a more accurate result than a blood sample, unless they are testing for other things like his hormone levels and what not. Other than that, a urine test may also be able to provide some insight at the biochemical level, but the sperm sample would be the most important step. If you're both okay with the idea, I don't see what should stop him from doing it, except that it does create a weird situation for the child where they have two dads and both of them are also their uncle. Add a generation and, OMG, you get two uncle-grandpas! :o

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  • 2 months ago

    i believe they test sperm

  • LizB
    Lv 7
    2 months ago

    There are some genetic conditions that can make men infertile or sterile. Can't think of any reason an RE would want to test family members, though, since if your BIL is sterile due to a genetic condition they could diagnose that through his own test. Sure your fiance isn't getting tested just because he wants to know his own fertility status?

  • 2 months ago

    The only person who can answer your questions in your fiance.  You really don't want to be marrying someone who hides things from you, particularly if he is going to father someone else's child.  That should be a discussion and decision you make together.

    As others have noted, infertility would be based on sperm count. I'd assume anyone donating sperm would need to have some tests done to rule out any health issues,  but standard blood panels don't include genetic screening. 

  • 2 months ago

    They need to check his sperm county for infertility and not his blood and we don't know if fiancé is donating his sperm, you have to ask him

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