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Polar exploration: small steps towards cheaper, safer, easier IVF?

A new method of screening eggs for IVF has been developed, promising better chances of successful IVF cycles.

Two out of three women fail at each IVF attempt, and a large part of this is believed to be due to abnormalities in the number of chromosomes in the egg. Up to half of the eggs in younger women (and up to 75% in women approaching 40) have abnormalities. In traditional reproduction these failures would not be problematic, since attempts at conception can easily be retried. But in the case of IVF each attempt will be expensive and time-consuming. The new method is a small step towards truly efficient IVF. But does it solve the ethical issues?

In the past eggs would have first been fertilized, then a cell removed
from the embryo, the embryo would have been frozen and, once the tests
on the sample cell were in a few days later, one of the frozen embryos
would have been implanted. While this gives plenty of time, it involves
the deliberate creation of some embryos that will be discarded –
something many have objections against.

All normal cells except egg and sperm contain 23 pairs of chromosomes. Eggs and sperm just have one copy of each chromosome. When an egg develops it throws away the unwanted chromosomes into a small compartment, the polar body. The new method makes use of this. The polar body can be picked up by pipette in the lab, and subjected to chromosomal microarray analysis, a method that detects whether there are extra or lacking chromosomes. The answer is back within a day, and only eggs with 23 chromosomes will be fertilized and implanted.

Improving IVF like this not only saves effort, it may also reduce the number of twins and triplets born (since, as a precaution against the expected loss, currently several embryos are implanted). Twin pregnancies have a higher rate of complications, so making single pregnancies more common would benefit the children too.

However, while a step forward the this method is not likely to appease people who think personhood starts at conception. It only allows avoiding creating embryos known to suffer chromosome abnormalities. Not all of the embryos that are created will be implanted, leaving some of them frozen or discarded, so the improvement is mainly in a reduced number of extraneous embryos.

Is this method selecting for enhanced or at least normal offspring? Not really, since the vast majority of embryos with abnormal chromosomes would not have implanted. Yet the microarray analysis seems to technically enable selecting eggs based on particular genes. This would not be a reliable way of getting desirable traits since the genes contributed by the sperm are uncontrolled, but it would allow selection that statistically favor some traits. It would also get around some of the ethical objections made against post-conception selection: there is no selection away of persons, since (to my knowledge) nobody argues that personhood can begin before conception.

However, just as I doubt avoiding creating some extraneous embryos will not make the personhood-at-conception people happier, I doubt this form of pre-conception selection will make the anti-selection people happier. The real concerns are little affected by technicalities and more on the overall meaning of the activity.

But improvements of the efficiency, safety and cost of IVF are nothing to sneeze at. Much of progress occurs in small steps rather than dramatic breakthroughs.

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1 Comment on this post

  1. We have been able to analyze the polar bodies thrown off pre-fertilization for some time, but the last polar body is normally only released after fertilization. The article isn’t clear on whether the procedure is removing that last body (although it would make most sense if that is what they have developed).

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