How much can pre-conception genetic testing tell you?

In the “can a child ask for a paternity test?” thread, more than one person suggested that pre-conception genetic testing could tell the OP a lot about their chances of having a child with genetic predispositions towards medical conditions.

How much can they tell you? And how? Does it work by telling you if you, the potential parent, are a carrier? Does it work for mental illnesses too, or just physical ones?

I ask because one of my reasons for being highly ambivalent about having biological children is that I don’t come from particularly healthy stock. I’m fairly healthy, but I don’t think that means I’m not possibly a carrier for certain conditions.

Suppose I found “the one” and he and I were to consider having a baby. Which of these things found in my family could genetic testing give us some odds on?

  • spina bifida (mild in Mom’s case but in a second cousin lead to hydrocephalus)
  • chrone’s disease
  • an off-shoot of sickle cell anemia I can’t remember the name of (one more common to certain European types rather than African types)
  • clinial depression
  • bipolar disorder
  • schizophrenia
  • psoriasis
  • diabetes (both types)
  • cancer (all four girls in my maternal grandmother’s family got breast(3) or ovarian cancer(1), and both m/f for generations prior died of various types though I’m not sure which. Mom’s had cervical, maternal grandfather died of liver)

And those are just the things I can think of off the top of my head.

I lucked out by not inheriting any of those things, at least so far (but am amongst the third generation of people on mom’s side to have baby teeth come in without enamel and never get certain permanent teeth, which is just odd) but I suspect that doesn’t put my hypothetical kids in the clear.

Anything that can be testing for by looking at DNA can be performed on fetal samples. In our lab, we do Fragile X, cystic fibrosis, and Rh antigen genotyping on fetuses on a regular basis, and any of our other tests could be run on them if the doctor had a good reason for ordering them. The DNA comes from fetal cells in amniotic fluid. Sometimes they’re cultured and we get a flask of amniocytes.

IIRC, my unborns were tested for everything that Smeghead mentioned, plus Down Syndrome and a couple of other chromosomal nightmares.

Both my SILs have been tested for the “breast cancer gene” and been negative (having it doesn’t mean you’ll get breast cancer, just that your risk is higher)- I don’t know if it is done on fetuses…

Many things just don’t have reliable, early tests yet, like schizophrenia and autism, espcially since those can come on at different times and aren’t necessarily visible at birth.

I have no autism in either branch of the family, but my youngest is mildly affected- go figure.

Unless you have something specific that puts a fetus at risk, you just have to cross that bridge when you come to it.

I only know about a couple of classes of these conditions but I have personal experience with both. The mental health conditions generally cannot be tested genetically at this time. However, studies show there is a genetic component(s) in there somewhere for most of them. I am bipolar and only after I was diagnosed did I find out that my maternal uncle killed himself from it and there is a huge line of what appears to have been bipolar disorder on my mother’s side going back generations. There is no clean lab test for that. Clinicians and counselors usually draw up a family history chart based on what is known through prior diagnoses and reported behavior. The same holds true for things like alcohol abuse and certain types of drug abuse.

My baby daughter died last summer of one of the most unlikely genetic diseases in the world. No test existed but researchers at Harvard Medical School and labs all over the world worked overtime to develop a test for a future child in utero. They fulfilled their promise because we have a daughter due in less than two months and and their risky in utero test proved that she did not get the 1 in 4 chance of having sulfite oxidase deficiency genes. Today, we have this custom test that could be used for preconception counseling but there have only been 50 cases ever reported worldwide. The disease is 100% fatal withing weeks after birth or completely debilitating and then fatal within a few years. We know both of our family’s ended up with the genes and family members have high odds of carrying the disorder. Our other children will need to be tested along with their potential spouses 20 or more years down the road because the results are dire if they both carry the gene no matter how unlikely.

There are many of those types of disorders floating around and the cost and financial and emotional expense in the case of a false positive is not generally worth it. The universe of disorders to screen for is pretty well defined for lab tests based on the advantages and drawbacks, For many other issues, you have to rely on a family tree and things that have been reported throughout the family and for many other issues, you have to take your chances unless you have a good idea of what you are looking for. They cannot test for everything even when such genetic tests exist for limited uses.

Shagnasty, I feel for you.

Hello - IANADoctor, but I work in the Infertility Medical Sector with a large number of Fertility Specialists (i.e., Reproductive Endocrinologists).

There is a procedure called PGD - Preimplantation Genetic Diagnosis. Here is the Wikipedia entry for it. (I have not had an MD review this entry in detail and canno vouch for its accuracy). Basically a woman’s egg is fertilized in vitro (i.e., outside the human body) and cultivated into an blastocyst - an embryo with 8 or so cells only. One of those cells is extracted and can be tested for a variety of genetic conditions, such as Down’s Syndrome, Cystic Fibrosis, Tay Sachs, etc. Conditions such as Bipolar or alcoholism, to my knowledge, can NOT be tested for.

Some otherwise normally-fertile couples undergo IVF (in vitro fertilization) explicitly to go through PGD before implanting an embryo based on one or both of their genetic pre-dispositions.

I hope this helps or at least points you in the direction of further research…

I think the OP is asking about pre-conception tests, ie genetic tests on the mother and father for potential genetic diseases that could affect any children they might have.
It is of interest to me as I happen to know I am a carrier of one of the more common genetic alements. As a carrier it doesn’t affect me much, but it would not be very wise for me to have children with another carrier as the 1/4 chance of having a child with the full blown condition would be a high risk for something that can limit lifespan and health of that child. The way I found out about this was that my Mom has had the full blown condition diagnosed recently, and so I took the relivent tests to see if I were a carrier or had the full blown disease, luckily I seem to only be a carrier.
I would be keen to know what other genetic diseases are out their that I could be screened for to see if I am a carrier of any of them.

There are hundreds, if not thousands of them. Given the cost of testing and the rarity of the majority of the diseases, it’s generally not a good idea to go testing for things at random. Generally, testing isn’t appropriate unless there’s some reason to suspect there may be a problem, like the family history in your case.

Thalassemia?

Although I believe there is some evidence to suggest there are genetic predispositions to these diseases, there haven’t yet been any tests developed for them, so at the moment (barring any scientific breakthroughs) you couldn’t be tested to see if you carry genes that could pass on a predisposition to your children.

If this is thalassaemia, I believe the genetics are well understood and you should be able to get tested to see if you are a carrier. Even if you are a carrier, if your partner is not then your children would not get the disease.

This is a bit more complicated. It is known that in many cases there is a predispostion to diabetes (seperate predisposistions to each type) and recently some genes have been discovered for a specific, relatively rare type of diabetes (MODY ). However unless it’s MODY that runs in your family there isn’t a test you could have to determine if your children are likely to inherit a predisposition to diabetes.

There are known genes (BRCA1 and BRCA2) that predispose women to breast and ovarian cancer and you could be tested for these. However, there may be other genes that haven’t been found yet, so if one of your affected relatives could also be tested to confirm that they have either BRCA1 or BRCA2 and that their cancers aren’t due to an unknown gene (in which case there isn’t any test that would tell you if you’re in the clear). I would suggest you consider very carefully whether you want to have the test before going ahead though - some people want to know if they have a predisposition to cancer (please note, a predisposition does NOT mean you will definitely get cancer) so they can keep a more careful eye out, others would prefer not to have that knowledge hanging over their head. It’s also possible that a positive result might cause problems with health insurance at some point in the future.

It’s also worth mentioning that cancers with known clear genetic risk factors are the exception rather than the rule.

IIRC the only routine preconception testing is CF and hemoglobin electrophoresis to tell about sickle cell anemia. These are the only things that have high enough preponderance and are clear-cut enough to justify testing in most regular partnerships. While I’m sure you could test for a lot of things, there is ethical and scientific basis against testing in many cases. If there is a family history of a clear genetic disorder then it can be warranted. But you have to be able to do something with the information that you get.

For instance, if there is a family history of a dominant disease, one has to really consider if one wants to chance passing that on to a child. The operative example here being Huntington Disease – universally fatal in a sucky way by the early 50s, dominantly inherited. See Guthrie, Woody. Arlo (his son) had the option to get tested in his 20s and refused. He had a 50% chance of inheriting the gene and dying in his 40s, and he didn’t want to be faced with that. For a disease like that – if you knew you were carrying a gene that would give you bad cancer in your 30s or neurodegeneration in your 40s – would you want to have kids? Would you want to chance passing it on to your kids?

There are other troubling scenarios. I’m Ashkenazi. My wife is Ashkenazi. This leads to one of the exceptions where preconception testing becomes warranted as there is significant carriage of recessive alleles leading to fatal disease. Done through my department, we tested a few, including CF, Tay-Sachs, Gaucher, familial dysautonomia, and Canavan. Recessive diseases mean that if both parents are carriers, there is a 25% chance that the kids will be affected. So if one parent is a carrier, test the other parent, if both are affected do CVS or maternal-fetal sampling, and if the fetus is affected, one has to be prepared to abort midway through the second trimester.

That can be a big problem for some people. Especially for a disease like Gaucher Disease, which can be terrible and life-shortening or, given a different genetic background, can be almost asymptomatic and eventually treated with splenectomy. There is a debate in the medical genetic community as to what to do for Gaucher. Gaucher Syndrome is not an anomaly, either – many if not most genetic diseases can have a wide difference in degree of presentation. So what do you want to do with the information?

From the list of diseases in your OP, none of those except perhaps the cancer is a commonly tested genetic scenario. I’m sure you could find some tests to have sent off, but I would advise you that the data you get back from them will not be easily interpretable, to the level that it could dictate how you would manage conception planning and a pregnancy. All of them would be worse than the information you get from a Gaucher Disease test. Except in the unlikely scenario that you have an BRCA1 or 2 mutation or any of the other cancer syndromes, the most you would get is something like “You have an allele that may increase your risk of cancer by 10%.”

If you are concerned, mention it to your OB/Gyn at a preconception testing. I’m sure there are ACOG recommendations, although I’m not able to find them right now (a secondhand reference seems to indicate CF testing for everyone). If you are both Ashkenazi or of another small population (French Canadian, Pitcairn Islander, perhaps Sephardi, history of consanguinity in the family, etc.) speak to your OB/Gyn and maybe get a genetics consult. But the diseases in your OP don’t give enough of a basis to run out an justify a lot of in depth exploration (except perhaps for the cancer history but this is doubtful given that 1 in 3 get cancer anyway – a family history of cancer is significant if it occurs in young people, the same kind of cancer recurs, and especially if there is an obvious inheritance pattern) . The technology is always improving, and in a few years we may have better tests. But IMHO I’d seriously consider doing the bare minimum.

Another example from our lab is hereditary hemochromatosis. We have an automatic block on any testing for patients under 18 years of age. We won’t test them until after our genetic counselor has talked directly to the doctor. The reason is that even if you have the mutation, you won’t have any problems until you’re in your 30s or 40s at the earliest, and it’s easily treated any time before symptoms show up. Given the possibility of discrimination by health insurance companies if they know you have a harmful mutation, it’s smarter to wait until the child is old enough to decide for himself whether he wants to be tested. 90% of the time, once our counselor talks to the doctor, they cancel the test.