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Good News for Pregnant Needlephobes....
December 8, 2010 4:11 PM   Subscribe

Invasive amniocentesis and chorionic villi sampling (CVS) tests are commonly used to determine the chromosomal, structural and genetic abnormalities in fetuses. But could they eventually become obsolete? A Chinese study has found that a complete copy of the fetal genome exists in the mother's blood, suggesting many prenatal diagnoses could potentially be performed noninvasively. posted by zarq (30 comments total) 10 users marked this as a favorite

 
Wow, that's cool. Thanks for sharing!
posted by Sublimity at 4:15 PM on December 8, 2010


There is also some work to use similar methodology to detect rejection episodes for solid organ transplant patients. DNA from the donor is found in the recipient's blood (rather than fetal DNA in the mother).
posted by sulaine at 4:27 PM on December 8, 2010


That will be fantastic if it turns out to be a reliable diagnostic. Yay, science!
posted by Sidhedevil at 4:43 PM on December 8, 2010 [1 favorite]


That's nothing! A complete copy of the fetus itself exists within the mother's tummy!

And it comes out of her bellybutton.

That's what one of the big boys told me.

posted by Joe in Australia at 4:49 PM on December 8, 2010 [6 favorites]


Genotype != phenotype.

So far, epigenetics -- the idea that the disease can be predicted using host genomic information -- has only enriched genetic sequencer manufacturers and Taq polymerase suppliers.
posted by docgonzo at 4:49 PM on December 8, 2010 [1 favorite]


No kidding -- a direct-to-consumer DNA testing company that I use for my genetic genealogy research accidentally picked up my unborn son's y-chromosome in my spit sample a few years ago. I was about seven months pregnant at the time, and they were supposed to be examining my sample for my mitochondrial DNA, and had to double test it because of a previous lab error, which led to the discovery. (Here's a listserve post I made about it at the time.)

In other words, a tiny bit of my unborn child's DNA was not just in my blood, as this FPP is talking about, but was even observable in my saliva, and was even visible to a lab that was not set up to do high-tech medical testing! Direct-to-consumer spit-sample pre-natal gender tests at your local drugstore, in 3, 2, 1...
posted by Asparagirl at 4:54 PM on December 8, 2010 [13 favorites]


Your pregnant needles don't scare me none.
posted by mmrtnt at 4:55 PM on December 8, 2010 [1 favorite]


Whoops, HTML fail. Here's the right link to the listserve post.
posted by Asparagirl at 4:56 PM on December 8, 2010 [1 favorite]


New Scientist:
However, at present the analysis is too cumbersome and expensive for clinical use. "At this moment, it would probably cost $200,000 per case," says Lo. "Cutting costs will be very important." ...
Still, Bianchi believes that the bioinformatics involved in reliably distinguishing fetal from maternal DNA sequences from a blood sample may prove impractical for many clinical labs. She also points out that the latest estimates put the risk of miscarriage associated with amniocentesis as low as 0.06 per cent. "At some point, someone's going to need to do an elegant cost-benefit analysis," she says.
posted by benzenedream at 5:22 PM on December 8, 2010


docgonzo, you've got it flipped around. Epigenetics is not the idea that the disease can be predicted using host genomic information; rather, it's the study of phenotypic traits that arise through mechanisms other than germline genetic variation -- and thus one of the reasons that, as you correctly point out, genotype != phenotype when it comes to complex traits & diseases.

However, many of the devastating disorders that are tested for with amniocentesis are due to chromosomal abnormalities and thus can be predicted from genotype, so I think you may be overstating your case.

& Asapargirl -- wow.
posted by Westringia F. at 5:25 PM on December 8, 2010 [1 favorite]


I don't believe a blood test is considered non-invasive; saliva test might be but I'm doubtful.

Less invasive, definitely.

Very awesome; learn something new every day.

I wonder how long it takes to rid our bodies of it all. And what triggers it. Is it removed all along and when the baby is out you eventually lose it all? How soon can you detect it (how long after the right placental links are made, assuming that is the method of xmission). ?

Awesome.
posted by tilde at 5:36 PM on December 8, 2010 [1 favorite]


Oooh, wait -- more fun than OTC pre-natal spit sample fetal gender testing kits will be OTC pre-natal spit sample fetal paternity testing kits!

Maury Povitch should totally get on this: You Are (Not) The FatherTM test kits, available now at your local CVS or Walgreens!
posted by Asparagirl at 5:50 PM on December 8, 2010 [1 favorite]


She also points out that the latest estimates put the risk of miscarriage associated with amniocentesis as low as 0.06 per cent.

Yep. And potentially as high as 3-5%, I've learned. As you might expect, the risk of miscarriage may be higher from amnio or CVS when one or more are performed during an otherwise high-risk pregnancy.

My wife had two CVS tests run. (One per fetus.). We then had an additional amnio because the CVS sample from my son was nonviable. She was also on Lovenox and other drugs throughout.

Our perinatologist judged the risk for the CVS for two fetuses at about 3-5% and amnio at about 3%.

We'd have given a lot at the time to have had a reliable diagnostic blood test available instead!
posted by zarq at 6:31 PM on December 8, 2010 [1 favorite]


I heard someone say that they could not find any fetal DNA in mothers 48 hrs postnatal. This was in response to a question about whether they'd be able to diagnosis a trisomy when the mother had prior affected pregnancy.
posted by sulaine at 6:54 PM on December 8, 2010


my unborn son's y-chromosome in my spit sample a few years ago ... In other words, a tiny bit of my unborn child's DNA was not just in my blood, as this FPP is talking about, but was even observable in my saliva
Well, since the y chromosome comes from the father, without any changes, Isn't simple contamination a likely cause?
posted by delmoi at 9:44 PM on December 8, 2010 [1 favorite]


This is crazy town.
posted by maryr at 9:49 PM on December 8, 2010


I don't believe a blood test is considered non-invasive; saliva test might be but I'm doubtful.

Sampling the mother's blood would be far less invasive to the fetus.
posted by maryr at 9:56 PM on December 8, 2010


Well, since the y chromosome comes from the father, without any changes, Isn't simple contamination a likely cause?

Are you suggesting that ejaculate from coitus can somehow contaminate the female's saliva?
posted by hippybear at 10:02 PM on December 8, 2010


Hippybear: Obviously that's impossible, and in any event there's no way it could be present seven months later. Delmoi probably means "what if he kissed her and some of his DNA remained on her cheek, contaminating the sample at the time she was preparing it."

Yes. That is the way it must have gone dhappened.
posted by Joe in Australia at 10:28 PM on December 8, 2010 [1 favorite]


I don't believe a blood test is considered non-invasive; saliva test might be but I'm doubtful.

I know what you mean, tilde. When I had a saliva test they got all up in my face.
posted by StickyCarpet at 10:53 PM on December 8, 2010


delmoi, one is instructed not to eat or drink anything for at least an hour before using the spit swabs for that particular DNA testing company. And that certainly includes eating or drinking you-know-what, you cheeky monkey.
posted by Asparagirl at 11:14 PM on December 8, 2010


Actually, I'm third-trimester-preggo again right now, so I suppose we could just repeat the experiment with a fresh set of cheek swabs and see if we can find this baby's DNA in my spit. And I do actually have some extra swab kits at my house, because I'm weird like that. But this baby's a girl, so rather than looking for a y-chromosome, we'd have to look for an X-chromosome that isn't one of mine, which might be a little more difficult, but technically doable.
posted by Asparagirl at 11:21 PM on December 8, 2010 [1 favorite]


So far, epigenetics -- the idea that the disease can be predicted using host genomic information -- has only enriched genetic sequencer manufacturers and Taq polymerase suppliers.

Uh, epigenetics is much, much more interesting thing than this. The concept that there's an entire programmatic layer to genomic output, inheritable up to seven generations and responsive to environmental input, is rather significant.
posted by effugas at 2:54 AM on December 9, 2010 [1 favorite]


So far, epigenetics -- the idea that the disease can be predicted using host genomic information

This word doesn't mean what I think you think it means.
posted by rxrfrx at 4:28 AM on December 9, 2010


It does not seems a totally new discovery: as early as 1996 fetal cells were isolated from maternal blood and studied. Molecular genetic and cytogenetic testing were possible at least that early.
posted by francesca too at 5:29 AM on December 9, 2010 [1 favorite]


I'm third trimester pregnant, too! High fives!

I think a lot about how little I know about my daughter. More or less, I know just a few things about her: her name, her who parents are, that she is physically fairly normal, and that she is not deaf*. It's kind of astounding that there is so much more information that I could have about her and it's all sitting literally on the tip of my tongue.

Of course, as nice as it would be to know her hair and eye color in advance, these tests can't really address the questions I really want to answer. Will she be a quiet or loud baby? Will she like reading? Will she be an obnoxious teenager like her mom or a nice one like her dad? (and on to infinity)

For $200,000 I would at least want a chart addressing the probability that she will move back in with me during her 20s.

* I have a cardboard paper towel tube on my desk that I use to startle her into moving when she sticks her head into my rib cage. It works wonders.
posted by Alison at 7:36 AM on December 9, 2010


"Well, since the y chromosome comes from the father, without any changes, Isn't simple contamination a likely cause?"

delmoi, allow me to inform you of the crazy-ass shit that is PUPPP (Pruritic urticarial papules and plaques of pregnancy), a rash occurring during pregnancy that primarily happens to mothers of boys. If a scraping is taken of the rash and biopsied, they find the male fetus's DNA on the mother's skin. So I would not be totally shocked to find fetal DNA elsewhere in the mother's system.

My husband hypothesizes that the fetus is crawling out at night, rubbing itself all over the mother's skin, and then using its umbilical cord as a rescue rope to pull itself back in.
posted by Eyebrows McGee at 9:42 AM on December 9, 2010 [1 favorite]


Asparagirl and Alison, congratulations! :)
posted by zarq at 12:42 PM on December 9, 2010


I don't believe a blood test is considered non-invasive; saliva test might be but I'm doubtful.

Under the strict definition of "invasive" you're absolutely right. But my (laypersons) understanding is that medically-speaking, blood sampling is traditionally considered (and referred to as) non-invasive, especially when compared to truly invasive prenatal diagnostic procedures, such as a CVS test. Saliva sampling falls under the same category.
posted by zarq at 12:48 PM on December 9, 2010


PUPPP (Pruritic urticarial papules and plaques of pregnancy)

C'mon folks. This isn't the Infinite Jest/DFW thread.
posted by benzenedream at 1:22 PM on December 9, 2010


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