June 29, 2009
New Embryo Genetic Test Boosts IVF Success Rate
Assisted Reproduction Technologies (ART) keep getting better. In Vitro Fertilization (IVF) has a very bright future.
Amsterdam, The Netherlands: A new test examining chromosomes in human eggs a few hours after fertilisation can identify those that are capable of forming a healthy baby, a researcher told the 25th annual conference of the European Society of Human Reproduction and Embryology today (Monday 29 June). Dr. Elpida Fragouli, from the Department of Obstetrics and Gynaecology, University of Oxford, UK, and Reprogenetics UK, said that her team's work had already enabled seven ongoing pregnancies in a group of older women with a history of multiple failed IVF attempts.
I would not be surprised if some women in their late 30s go traveling between continents to go to Oxford to get access to this method of embryo selection.
"Out of 35 patients who had embryo transfers after the test, we achieved a pregnancy rate of 20%, which is exceptional considering the extremely poor prognosis of the women involved." she said. "This represents a doubling of the usual pregnancy rate for women who fall into this category, which is otherwise, at best, under 10% and, at worst, zero. To date, we have two live births from this group, and all the other women who became pregnant have maintained their pregnancies. The study is continuing, and we believe that we will achieve more pregnancies with the help of this technology in the future."
The scientists used the Comparative Genomic Hybridisation (CGH) technique to count the chromosomes in each egg. Unlike conventional screening strategies, using the fluorescent in situ hybridisation (FISH) method, which allows less than half of the chromosomes of an embryonic cell to be examined, CGH enables the evaluation of the entire chromosome complement. CGH was used to examine the fertilised eggs by looking at polar bodies, tiny cells that are a by-product of egg development. The chromosomes of polar bodies provide an indication of whether the corresponding egg is normal or abnormal; if the polar bodies have the wrong number of chromosomes, so does the egg.
Better tech for doing IVF embryo testing will make IVF more appealing as a way to create babies as compared to plain old-fashioned sex. We'll still have sex. It just won't be for making babies. Cheap genetic testing which yields lots of details about embryo genetic profiles will cause people to personally practice eugenics on a massive scale and the great human evolution acceleration of the last 10,000 years will pale next to the massive human evolution of the next 100 years.
At some point I expect IVF baby creation to become less risky than conventional sex as a way to start pregnancies that turn out well. That point is probably approaching in the next 10 years. Granted, women in their late 30s starting pregnancies will still run bigger risks of bad outcomes as compared to women in their early 20s. But the total risk will go down for all women using IVF and eventually genetic testing of embryos will become so powerful that IVF will yield smarter, healthier, better looking, and otherwise - dare I say it? - superior babies. Yes, I dare.
I think we're lucky to be living at the point in human history that will let us witness this change. In my case, I'm at an age at which it's practical to delay mate-seeking in order to wait for better reproductive tech.
For males, I think that delay is manageable for people of a range of ages if we freeze semen to minimize age-related degradation in quality. (Freezing eggs, on the other hand, seems like a more complicated picture with today's technology.)
Yes, a guy can have a much smarter baby 10 years from now. Not sure exactly when the cross-over is going to occur. But it is coming.
Sperm quality: We are eventually going to be able to fix that too. Ideally what we'd want to do is take many different adult cells, separate them down to a single cell, grow them up to make several of each starter cell, sequence one of the cells from each group, and then identify the group that has no serious mutation that developed since birth that needs avoiding. Then make the cells from that group divide into a much larger number.
Here's where it gets tricky: Take the individual cells from the best group and induce each cell to do meiotic division (split so that each has only half the normal genetic complement). Take a cell from each pair and genetically test it. We can then determine which chromosome of each pair is in the other cell. Do this for dozens (even hundreds) of cells. Figure out which cells contain the best genes for passing along. Then use their DNA to put into a egg.
Do that with maybe a dozen eggs. Test all the resulting embryos. Implant the most promising embryo.
Are IVF children going to get healthier? I seem to remember IVF kids have a shorter life expectancy.
Also, what is the big turnoff of just marrying a young woman who wants to have children? Seems like a cute 20 year old has more to offer than just eggs.
First off, women who use IVF today older and/or have reproductive problems for other reasons. So to start with their babies are going to have more problems.
Second, sure IVF has risks. One risk probably comes from an environment that causes more oxidative stress. Another risk is that there's no selection effect for sperm that can swim better to the egg. So there's less selection for healthy sperm. Still another risk has to do with using hormones to produce the eggs.
What I'm arguing is that if we start with healthier younger women with healther eggs and wombs and then add in genetic tests and better lab techniques to do IVF with less stress on the embryo then IVF can produce better results. I'm not saying that's doable today. I am saying it is doable within 10 years or so. IVF will become the lower risk option for starting a pregnancy.
Yeah, It just seems that healthy young women already have such good odds of having healthy kids, it is like a diminishing return unless you know you have genetic risk. It makes sense for both partners to get tested for genetic risk before getting pregnant. Then use IVF to screen out bad eggs if you have risk.
Everybody's different, and different marriage decisions are better for different circumstances. For me, though, I think there are some natural advantages to waiting to marry.
The older a potential spouse is, the better your measure is of who they are, and the lower the chances of being surprised down the road by difficult-to-predict epiphanies or changes in career performance. People in their 20s can sometimes change a lot.
Having a better measure of who potential spouses are doesn't just reduce the chances of divorce, it also gives us a better idea of what kind of cognitive temperaments our kids will possess.
sg, Even young women give birth to babies with birth defects. A California monitoring program finds birth defect rates bottom for women between ages 25 and 29 at about 1.3% which is still pretty high when you think about it. They show the rate rising to about 3% over age 39. But another measure finds 4.8% for live births in the United States.
Not all birth defects are obvious at birth. So I suspect that some monitoring programs might underestimate incidence. Also, some genetic defects do not cause problems until later. Does autism get counted as a birth defect? My guess is no. Similarly, there are genetic risks for asthma and other diseases that show up in childhood. So the number of problems avoidable via embryo selection is potentially very high.
"Another risk is that there's no selection effect for sperm that can swim better to the egg."
I really liked the idea that sperm competition might filter harmful mutations at the haploid level. Unfortunately, it doesn't appear to be true. The DNA in a mature sperm is tightly packed and is not expressed so sperm quality depends on the germ cell line that produced the sperm, not the DNA in the sperm.
Then I wondered if sperm competition could be filtering mitochondrial mutations. Nope. The egg has a hundred fold more mitochondria and in humans it appears that the mitochondria from the sperm are destroyed soon after fertilization.
So sperm competition is only important when different males are competing to fertilize the same female.
Some species have an extended haploid stage during which genes are expressed and selection does occur...but not humans.