Marrying cousins and genetic diseases

amother

Blonde

Mon, Mar 12 2018, 11:20 pm

I've been trying to google for information about this, but can't seem to find anything substantial, or at least anything I can understand. Perhaps someone here can help me out.

How much greater are the risk of birth defects and genetic diseases, if the child of two first cousins marries his/her second cousin?

I'll break it down like this:
A and B are first cousins, they are married
Their child C is going to marry D, a second cousin.
One parent of D is a first cousin to both A and B.
So out of four parents, three are first cousins.

How great is the risk of reproductive problems for couple C and D?

amother

Cerulean

Mon, Mar 12 2018, 11:26 pm

I am not sure that anyone could give an exact percentage chance for their children having a disease. But the chance are very high. There are a lot of cousins marrying each other in communities like Monroe and other chassidishe circles. Their offspring are know to have a higher chance of having a genetic disease. The Amish have the same tendency for the same reason. There are those who don't marry a someone if they know that they are related.
Nowadays there are all sorts of testing for genetic diseases called carrier screening tests they can both do before getting married but they only test for diseases that are currently known about. These people may be a carrier for something else.

Frumwithallergies

Mon, Mar 12 2018, 11:36 pm

This is a delicate situation. Has the shidduch been made already?

In general, the above scenario increases the risk of transmission of 'recessive' diseases, namely diseases for which both parents are carriers of a gene, each passes their gene to their child, and the child expresses (has symptoms of) the disease because they inherited two copies of the same gene.

Cosanguinity (inbreeding / cousins marrying cousins) increases the risk of recessive diseases in the Jewish community (such as Tay Sachs, Charcot-Marie-Tooth Neuropathy).

In many communities, there are organizations that offer genetic counselling. Please consider consulting such an organization rather than looking at Dr. Google.

Hope this helps!

amother

Coral

Mon, Mar 12 2018, 11:37 pm

amother wrote:

People in Monroe?
This is actually very rare. Happens by some very Rebbish ultra people. Some of them may live in Monroe, but as for the general population this is basically unheard of.

amother

Papaya

Tue, Mar 13 2018, 12:47 am

amother wrote:

If they will be doing dor yesharim and there are no unhealthy relatives then it should be pretty safe. I recently read that most ashkenazi genetic diseases originate very far back so it is not so much a family thing.

OMG, this is so wrong!

amother

cornflower

Tue, Mar 13 2018, 1:33 am

Cousins do have a slightly higher risk of genetic diseases and still births, but the risk isn't that high.

Still, why go into a marriage with increased risk? Not to mention the emotional mess created when you are related in two ways.

If cousins meet and fall desperately in love, that's one thing. But to deliberately set up a less than optimal situation seems like a bad idea.

DrMom

Tue, Mar 13 2018, 1:41 am

amother wrote:

I'm trying to get some scientific evidence as proof of this increased risk to convince some of the family about how wrong this is. I know the chances are greater, but how great, and is it significant enough to have a discussion about.

According to a various studies (links in articles below) article, the risk of a genetic defect is approximately double, increasing from 2-4% to 4-8% (depending on the population studied).

Different publications have interpreted this finding differently. Some have headlines like:

Quote:

Marriage between first cousins doubles risk of birth defects, say researchers

https://www.theguardian.com/sc.....fects

Others like this:

Quote:

Few Risks Seen To the Children Of 1st Cousins

http://www.nytimes.com/2002/04......html

This article argues that although the risk doubles, it is still low.

***Since you know the specific people involved, have you suggested genetic testing?

Most of the increased risk is due to sharing the same genes which, if there is some defect, are even more likely to be similar defects (since the two parties are related), and thus express a genetic issue which may be recessive in each of the parents' genomes.

But if two people involved undergo genetic testing, the lab can calculate the risk for this couple specifically, the same way they would for any two unrelated people.

Mamushka

Tue, Mar 13 2018, 3:39 am

Why don't you ask a specialist in this field. This is the only way to get an accurate answer.
My friend who is a specialist in the field says that the risks aren't much higher. Saying this, it's a general statement. Talk to the doctor. Give details of the family. Get an accurate answer for your specific situation.
Good Luck

PAMOM

Tue, Mar 13 2018, 7:35 am

Dr . Mom’ s explanation was very clear. A family member of mine consulted a geneticist in the medical school affiliated with her college about a similar situation. His answer was essentially the same. He also added the caveat about doing genetic testing.

amother

Olive

Tue, Mar 13 2018, 7:50 am

amother wrote:

I was on vacation once with a Belzer and she said that cousins marrying is common in her circles.

This is true. My husband is Belz and his parents are first cousins, as are one set of grandparents. My kids are not marrying anyone related. Just to be perfectly clear.

ally

Tue, Mar 13 2018, 7:57 am

DrMom wrote:

The problem with directly applying these studies is that they do not necessarily account for prior inbreeding. So the risk factor for two first cousins who have no prior history of intermarriage in the family will be lower than that of two first cousins who are also related to other degrees- which is more likely to be the case in close knit communities.

I also am hesitant to think that current genetic testing is the absolute be all and end all. We are far from fully understanding the genetic component of many diseases.

happyone

Tue, Mar 13 2018, 8:37 am

mama24 wrote:

Dor yeshorim should b done (by any shidduch) to check for any genetic diseases and if they are compatible. If the risk is to high they will see

dor yesharim is very limited in what they test. They should go through Jscreen or counsyl if they were to proceed. It's way more comprehensive .

amother

Fuchsia

Tue, Mar 13 2018, 9:30 am

amother wrote:

This is true. My husband is Belz and his parents are related....

Everywhere there are people that are ok with this type of thing. But to say it's common in.... I don't think so at all. They (the family) do it. Finished.
I just love how people blame their society for the things they're doing.
I was once visiting someone in Israel and there where some other people there (I never met). They where talking about giving ugly names to kids after a grandparent. Some said they would cuz that's how the grandparent was named and that's how it works. Others said they would never give an ugly name and that it's mean to the kid. Others said they would add another nice name to it. Anyway, so one American lady started saying how you have to name after a grandparent, no matter how they where named and she never heard of "not liking a name, it's not an excuse"
She said: "in America everybody names after their grandparents. There they know no chochmes! I hv friends that gave weird and ugly names to their kids cuz that's how the grandparent was named. In America everybody does it. And they are right. That's how it should be". Everyone believed her. Later I talked with my mil about it and she said "the Americans know of no chochmes they give the name they have to give and finished". I had a good laugh. People just believe everything. She (American lady) thought that was the right thing to do and her friend thought so too, doesn't mean that'show it's done in America!!!! Chatterbox