suppose there are some sort of restrictions against the practice of creating embryos using IVF for subsequent implantation. Instead, could sperm be subjected to filtering (such as to filter out the ones with the right gender or, more speculatively, right allele for a condition for which the male is heterozygous) and then applied using the classic artificial insemination?
Livestock breeders can buy sexed semen for artificial insemination, so it’s certainly technically possible, at least as far as gender goes.
Is it possible to do that with humans? Say if I want to have a boy or a girl, I can? If so, that’s pretty awesome.
It’s illegal here (Australia) and some other places, although most make exceptions in the case of genetic disorders that are gender-linked. People have travelled to the US so they can have the boy-or-girl of their dreams without the risk of being stuck with a girl-or-boy of the gender they didn’t want. Sex-selection tourism.
Girl sperm are heavier than boy sperm because the X chromosome is larger than the Y chromosome. By placing semen in a centrifuge, all the girl semen go to the bottom. You can either take the semen from the bottom (and have a girl via artificial insemination) or from the top (and have a boy via artificial insemination).
At least that was the methodology when I last heard about it a few years ago. Accuracy was about 90% as I recall. I’d imagine it’s better now.
It’s not anywhere near that good: I’ve heard claims of 90% for a girl, but closer to 70% for a boy, which, considering you start out at 50%, is not that good. Certainly not good enough for people looking to avoid a genetic disorder. Fertility medicine is a big business, and clinics are quick to adopt technology that works–genetic analysis of embryos prior to implantation was revolutionary a decade ago, and I know of 10 different clinics in my city that offer it today. Sperm sorting has been around 20 years: if it really worked, it’d be available.
It would be impossible (with current technology) to examine each sperm for genetic information–running a DNA analysis destroys the cell. It’s possible to do this on a 5-cell embryo because you can take one cell without destroying it.
Many people don’t realize that artificial insemination has a very low success rate, even under ideal situations–something like 8-15% per round. Spinning out a huge chunk of the available sperm (since I assume you take the top or bottom 10%, not the top or bottom half) can’t help. Now, it’s relatively cheap, ($500-$1500 per round) but once you add the price of “sorting” the sperm, it’s not nothing, and if you have to go 5 rounds–which is not implausible–you may be close to the cost of IVF. IVF success rates are significantly higher(60% or more for someone with no complicating factors), and if you are looking to avoid a fatal or painful disorder, it’s much more certain.
I’m surprised the success rate is so low in humans, since AI is standard in livestock and not uncommon in dog breeding. That said, IVF and embryo transfer are much difficult and unsuccessful in livestock. It is done in some segments of cattle industry, but I don’t think it has had any success in horses and dogs.
So basically, the rich can decide if they want boys or girls, the rest of us have to hope for the best?
A round of IVF + PGD (the technology that screens embryos for sex) costs 10-20K. This is expensive, yes, but you’ll pay more than that in various expenses during most years of your child’s life. Expensive, yes. Unattainable for all but the rich? Hardly. Many, many “non-rich” people drive cars more expensive than that.
I have no idea why insemination is so much less successful in humans, but I would guess it has something to do with the fact that dogs and cattle both are more likely, in general, to become pregnant as the result of a single sexual encounter.
I’d WAG, too, that people are willing to take risks with livestock that wouldn’t be acceptable to humans.
Manda JO, thanks for the clarification of why embryo selection is the only way to pick the “right” genotype at the present. Ignorance fought.
About artificial insemination, so do they have ways to make it work better with cows than with humans? After all, 15% chance of getting a cow conceive doesn’t sound like good business.
I do know that they monitor the estrual cycles of the animals involved, and time the AI precisely in the window that will coincide with ovulation. It is also likely due to, as Manda Jo mentioned, they are more likely to conceive after one cycle than humans (particularly horses). What strikes me as weird is that IVF in humans takes much more easily than in animals, it seems.
It is an interesting (although a bit icky) field, theriogenology. They’ve figured out the minimum amount of sperm needed to fertilize one egg, how much they need per straw, how many abnormalities are acceptable before having a bad sperm sample, etc. I’d think many of these things (testing the sperm, how much is needed, quality) are standard in humans too.
keep in mind that for humans the subset receiving artificial insemination is self-selecting, and generally from the population that has fertility problems.
For animal it’s generally the healthiest and most desireable portion of the population that has IUI performed. (it’s mainly a matter of convenience so that they don’t have to ship that ultimate stud bull around, and deal with the attending issues of breeding him at the right time, dealing with aggression, timing, etc).
There are multiple steps in achieving pregnancy. You may achieve insemination without fertilization. You may achieve fertilization but not achieve implantation. You may achieve implantation, but have a defective (non-viable) embryo that spontaneously aborts (or unfortunately in some cases doesn’t).
IUI (intra-uterine insemination) helps you get around the issue of timing the insemination. You monitor (or in some cases force) the timing of ovulation, and then inseminate during the optimum window for fertilization. Fertilization, implantation and all the rest are still a crapshoot, though you have an opportunity to filter, screen, and wash the semen for optimal performance.
IVF guarantees fertilization, and gives you a chance to screen the resulting embryos based on their growth patterns- or even (very expensive) based on genetic screening of the embryos. Implantation is still a crapshoot (I think 30% is the norm - but it really depends a lot on the subject). You can still have embryos that fail to implant, or do implant and fizzle. Generally younger is better when considering the odds.
I’m not sure about IVF, but embryo transfer is used (reasonably) successfully in horses, both for mares who have trouble carrying a pregnancy to term and for mares who are perfectly healthy but whose owners want to continue competing them in the show ring or get more than one foal per year. For owners with no suitable recipient mare, there are several equine practices which have large recipient herds of healthy mares for embryo transfer.
Thanks for the info. Maybe it was my mistake confusing IVF with embryo transfer (where the fertilization may still occur in uterus and the embryos “flushed out”). I remember the lecture talking about being able to do one (embryo transfer), but not the other one (IVF).