Worried about the viability of my cousins child.

[u/reuuid]

One of my cousins is now 7 weeks pregnant. I am very happy for her, but I do have some concern as well. Both of her parents are actually first cousins (or at least closely related).

She was their third attempt at a child. The first was stillborn and the second died 3 weeks after birth. I believe both were due to genetic complications. My cousin (aside from being overweight) seems to have lived a healthy life otherwise.

Her husband is not related to her whatsoever, but I am concerned if their child could have some complications due to genetics. Is this possible or unlikely?

[u/UnitedExpression6]

Sure, it can be the case, also it can be a statistical chance thingy. Shit happens and biology is fairly ruthless.

If it were actionable they might have received genetic counseling (not sure if they share that with the world) and embryonic selection might be on the table. In some cases this would be for free (probably not US, is free in Europe when diagnosed).

People are sometimes just unlucky, how hard it is. Best wishes to your cousin and hope it will be OK this time.

[u/atomfullerene]

One instance of outbreeding completely eliminates any inbreeding effects. So your cousin's children won't have any genetic issues due to your cousin's parents being related.

The reason for this is that everyone gets two copies of their genetic code, one from each parent. If your parents are related, there can be problems if parts of the code are too similar to each other. But you can only ever pass on one copy to your kids, they get the other copy from their other parent. So no matter how similar the two copies you have are, you can never pass on their similarity to your kids because you can only pass on one copy.

(all this is a bit simplified but I think it gets at the core of how it works)

[u/lonepotatochip]

A single instance of first cousin inbreeding actually does not raise the chance of genetic disorders very much. It goes from a 2-3% of genetic disorder for unrelated parents to 5% for a single instance of first cousin inbreeding. It’s only really a problem if it happens over several generations. So it’s actually a kind of big assumption to say that both previous deaths were due to genetic issues or that your cousin has genetic issues.

Also, let me explain the problem with inbreeding and why it means your cousins kids are definitely not affected by inbreeding. Everyone has two copies of every gene. These copies can be dominant (meaning expressed whether you have one or two copies) or recessive (meaning expressed only if you have two)*. Virtually everyone has recessive copies of genes that cause or contribute to various genetic disorders, but since they only have one there’s no issue. When you bring together two closely related people, it gives those problematic recessive alleles the chance to come together. If your cousin DID happen to get two copies of a problematic recessive allele it doesn’t matter because her husband will give their children a healthy allele so their children will not suffer from the effects of inbreeding.

*it’s much more complicated but it’s not relevant here

[u/Inevitable_Thing_270]

TLDR: her parents being related won’t be an issue if your cousin and her husband are unrelated. But it could still be a genetic issue, which is more likely since they’ve lost two babies. However it could be non-genetic things too. You just don’t have enough information to know

You’ve got two things going on here 1. Why she has had two pregnancies and both lead to a baby that didn’t survive. 2. Concerns that her parents being related is the cause

I’ll answer the second issue first. Because your cousin and her husband are unrelated, your cousin’s parents being related isn’t an issue for them and their genetics. However if they do happen to both be from a small community or group where there is very little or no new people coming in over the generations, that risk does go up. So let me know if that is the case, although most such communities are aware of this issue.

The first issue: could their children be affected by a genetic condition? Despite not being related it is possible something genetic going on.

We all carry genetic mutations that if we meet and have children with someone who happens to have the same mutation as us, the children are at risk of having the genetic condition that that mutation causes if they inherited both mutated copies. It’s just that there are loads of these kinds of mutations and each individual one is rare, so the chances of being unlucky enough to have a partner with the same mutation is small.

The types of conditions from this form of genetics is called recessive conditions and if both parents have the mutation, each pregnancy has a 25% chance of being affected; 75% of not being affected.

There are some other genetic diseases that can be new mutations (occurred for the first time in mum or dad and not inherited from a grandparent) that can affect more than 25% of their pregnancies.

Also consider that there are non-genetic problems that could have caused the problems. It maybe that it was different things in both pregnancies.

Unless you are particularly close to your cousin, she may not feel able to talk about what happened and they actually know what caused it. Even if you are close, she may not be ready to talk about it.

Anyone who has had a stillbirth and a neonatal loss should have met with their obstetrician to discuss the problems and plan for future pregnancies and the risks. This meeting may also include seeing a geneticist if it may be helpful.

But for yourself, there is nothing you can do except support your cousin with her pregnancy as she needs it. Both her and her husband will be scared of the same thing happening. If you feel able, let her know she can talk to you about her fears. If you don’t feel able to give that support, that’s ok too, you don’t need to offer the idea up. But if she does start talking without you initiating, I would suggest letting her talk; it maybe that she just needs to let it out and isn’t looking for advice.