Genetic testing before pregnancy

[greencrayon]

(DH and I are not really trying to get pregnant, but I've been off BC for about six months.)

So DH's brother has Prader-Willi, which is a disease where he's missing part of his 15th chromosome. I really didn't think anything of it, but at Christmas, I found out one of his cousins is also mentally disabled. So two out of five kids in his generation are mentally disabled. Is this something you'd be concerned about? 

[jewel]

Prader Willi and a non-specified cognitive impairment are very different, and likely totally unrelated. Many cognitive impairments are unexplained, but conditions like PW are almost always caused by random chromosomal deletions. These deletions are random events, and it is generally accepted that there is no explanation or way to predict why a genetic change happens. Some imprinting disorders (which includes a very small % of PW cases) on occasion, can be hereditary. Advanced maternal age also puts a person at greater risk for some conditions, but again, there is no way to test this risk before pregnancy.

Many non-specified cognitive impairments cannot be explained genetically, even in the individual affected. In these cases, there is definitely no way to pre-test parents, and would even show up clear on an amnio or other prenatal testing.

In situations like this, pre-testing is often unavailable. If you are worried about a specific disorder, especially if it is an imprinting disorder, you may be able to get some testing. The test results still won't tell you if anything will be passed on, just that it is a possibility. I'd recommend talking with a genetic counselor, if you're worried. Genetic testing is really infinite, so any pre-testing you might do would be only for specific disorders.

The real question is: what would you do with this information? If your husband is at risk for passing along a Prader Willi gene, would you consider trying to have a child in another way?

Personally, I would not be worried....any more than anyone else.

[greencrayon]

That was incredibly well written and reassuring. Thank you! I just needed to know if I was being silly or not. But if it were an issue, both DH and I are open to adoption.

[Cheesecake]

Jewel had an awesome response, I have this to add.

I think, unless you do genetic testing on IVF embryo's there is no way of knowing anything for sure until you do an amnio. And doing genetic testing on an embrio prior to implantation can actually cause defects as well, which is why generally they only offer it when the disorder you're testing for really is far far worse than what it could cause (so basically things that have a super high mortality rate). If you're not doing IVF, the only reason, whether or not someone carries a gene, to know if something is wrong, is by doing an amnio. Again, amnios bring their own risks with them as well.

To me the ultimate question with testing is: "Would I be willing to terminate a pregnancy because of this?" If the answer is no, I won't test.

(I have a genetic disorder myself and I know the chances are 50/50 that I'll pass it along to my children. I won't be testing for that and will take my (or rather his/her) chances with it. I asked myself if this disorder makes me regret being born, and it doesn't. The disease sucks, but besides that (and now the IF stuff) my life surely is worth living.)

[jewel]

Feb 9, 2013 23:30:57 GMT -5 greencrayon said:

That was incredibly well written and reassuring. Thank you! I just needed to know if I was being silly or not. But if it were an issue, both DH and I are open to adoption.

Not silly at all!

Even "if it is an issue" can mean different things, depending on the disorder. If my husband and I were both carriers of Cystic Fibrosis, for example, we'd have a 50/50 chance of having a child with CF. I would NOT take that risk. We'd have to talk about IVF with embryo testing, donor sperm/embryo, or adopting. However, I've met several people who have had one child with CF, and go on to pursue other pregnancies knowing their odds.

If your BIL does have an imprinting version of Prader-Willi, AND your husband also carries that gene, your chances increase only slightly. These are arbitrary numbers, but you may go from something like 1 in 30,000 to 1 in 25,000. Those odds are still good, and would not change my TTC plans in any way. To put that in perspective, the rate of Autism is currently 1:88, at least. On the other hand, children who are adopted also have a slightly higher rate of medical and developmental problems. (My point with all of this is that there is always a risk, either way. For any situation that puts you at only a *slightly higher* risk, if you plan is important to you, whatever it is, I wouldn't likely change)

I would always recommend pre-testing to anyone who has a known recessive disorder anywhere in their family. Most OB offices will offer testing for conditions related to specific ethnic groups (CF, Tay Sachs, Sickle Cell, etc), but not until you are already pregnant. If you are planning on doing that testing, do it BEFORE you get pregnant. It's much better information that way.

[degal99]

Feb 10, 2013 23:59:48 GMT -5 jewel said:

Feb 9, 2013 23:30:57 GMT -5 greencrayon said:

That was incredibly well written and reassuring. Thank you! I just needed to know if I was being silly or not. But if it were an issue, both DH and I are open to adoption.

Not silly at all!

Even "if it is an issue" can mean different things, depending on the disorder. If my husband and I were both carriers of Cystic Fibrosis, for example, we'd have a 50/50 chance of having a child with CF. 

If both parents are carriers there's a 25% chance of their child having the disease, it's 50% for their child to be a carrier.  I don't mean to nitpick, but punnett squares are my favorite.  

[degal99]

My RE's office has a genetic counselor on staff, and they offer a counseling session to everyone who comes in the office. I'm not aware of any risk factors with my or DH for the most common diseases. And even though I'm of Jewish descent, DH is not, so I'm not concerned on that front either. So we're choosing not to do any testing.

jewel gave you some really good advice. If you have the ability, it's not a bad idea to ask a genetic counselor.

[jewel]

Feb 11, 2013 19:03:08 GMT -5 degal99 said:

Feb 10, 2013 23:59:48 GMT -5 jewel said:

If both parents are carriers there's a 25% chance of their child having the disease, it's 50% for their child to be a carrier.  I don't mean to nitpick, but punnett squares are my favorite.  

Shiiiiiiiiit, that's embarrassing. You can fire me, right now.