February 26, 2014
A Better Fetal Genetic Test

In an article about a hugely improved genetic test for fetal DNA an interesting fact gets revealed: Lots of free-floating DNA in a pregnant woman's blood comes from the placenta around the fetus.

The screen analyzes blood from women who are at least 10 weeks pregnant. At that point, about 10 percent of DNA in the blood will be fetal DNA from the placenta, Dr. Bianchi said.

One consequence of very accurate fetal DNA testing: more abortions due to genetic defects. In any society with legal and easily available abortion services the amount of genetically defective babies will go down. I'll leave it to you all to form your own moral judgments about this.

Genetic selection by abortion is very inefficient and I expect a big shift to in vitro fertilization (IVF) combined with extensive pre-implantation genetic testing. This shift will start within 5 years whether or not the medical regulatory system supports it. People will travel abroad if they need to because the benefits will be so large. By selecting between several fertilized eggs prospective parents will be able to get more of their preferred chromosomes passed along. The result: smarter, better looking, healthier kids with personalities more tuned to success.

The upper classes especially will prefer to start pregnancies via IVF. Look at how much they spend on private schools and supplementary private lessons and learning experiences for their kids.

Genetic markers associated with about half of intelligence differences have already been found. An offshore clinic could start offering embryo genetic screening today if they could find a company willing to build them the gene chips they need to do the testing.

Share |      Randall Parker, 2014 February 26 09:46 PM 

joe said at February 27, 2014 12:05 PM:

Only someone who has never been through IVF could think this will happen soon. Unless success rates go over 75%. Going through IVF especially multiple cycles is really rough. 50% of pregnancies end in miscarriage. Self injecting 2x a day for a month and then have a miscarriage is really hard on a women. PGD is very limited right now, they just test for one gene or chromosomal abnormalities. There are better tests in the pipeline, but they aren't widely available yet. Even with better tests getting success rates up is key, I think it has to be more likely to work then the old fashioned way, plus give better results, to make the onerous process worthwhile.

David Friedman said at February 28, 2014 12:52 AM:

(I thought I put this comment up already, but it isn't appearing)

Genetic selection works a lot better if you can select egg and sperm separately, then combine. The obvious problem is that you can't analyze the genetics of a gamete without damaging it.

The solution, proposed in an early Heinlein novel, is to produce the gametes in vitro, capture the extra bodies—each gamete has only half the genes—and analyze them. Analyzing any cell gives you the full genotype, subtracting what isn't in the gamete tells you what is.

According to a recent BBC story, an early version of this is now being done as part of IVF.

ErisGuy said at February 28, 2014 8:30 AM:

The cost is too high for natural pregnancy followed by frequent rejection until the spawn is “just right." Improved IVF is the only realistic option for quality spawn.

Abelard Lindsey said at February 28, 2014 10:57 AM:

Joe is right. IVF efficacy rates have to increase before this scenario will play out. IVF is rather rough on the woman doing it.

ron said at March 1, 2014 3:09 PM:

Although do keep in mind that low IVF success rates are already selection-biased by the fact that most of the time it's much older couples who are using it.

jpstraley said at March 3, 2014 9:52 AM:

According to my Spec Fiction scenario, all this should be a integrated, tax-credit scheme. One of the first things to do is to collect gametes from men and women when they are, say, 16-20 years old. These are preserved on a little pad of liquid N for the next forty years, as which time they are either destroyed or the owner begins paying full fees. Amniocentesis (or the scheme of testing fetal DNA from a material blood sample--neat!) and free RU486 if required is the next piece. DNA testing (think "23 and Me")will help increase citizens' self-knowledge and inform important decisions. There's more, but that's a big start. Fewer genetically handicapped persons and more highly fit persons is a big payback from such a program.

Randall Parker said at March 6, 2014 11:48 AM:

David Friedman,

I can not find the BBC story that you speak of. Can you remember any terms in the article that would help when searching for it?


What is the purpose of collecting the gametes when someone is young? To boost their fertility when they are older?

My guess is that by the time it could come to use the the gametes it would be better to take some adult cells from the same person, do genetic editing on them, and come up with far better starter cells for beginning a pregnancy.


The biggest problem with IVF is age of the woman's body, not age of the cells used to create an embryo. Therefore an older woman either needs rejuvenation or to pay a host to carry the baby to term. If memory serves from reading a blog post by David's son, David has a grandchild which was carried by a paid host.

Phillep Harding said at March 8, 2014 11:43 AM:

That much DNA in the woman's blood and the immune system does not try to destroy it?

Pretty amazing.

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