Array CGH: The First “Egg-Screened” Baby
Alas, the Brits have done it again! They gave the world the first IVF baby (the called test-tube baby) more than 30 years ago. Last year, they presented the first “breast-cancer-free” baby. And now, here’s their latest coup: the first egg-screening baby.
Welcome Oliver, the first baby ever produced using Array Comparative Genomic Hybridisation (Array CGH), a new technique that allows doctors to check eggs for chromosomal defects before fertilization. Chromosomal aberrations in embryos are responsible for a lot of miscarriages and failed IVF attempts and they are mainly due to defects in the eggs.
During Ovulation
The egg has to discard duplicate copies of its chromosomes to give space for sperm chromosomes during fertilization. The discarded chromosomes are contained in a small cell called a polar body. Sometimes, something goes awry, producing an egg which has too many or two few chromosomes. Down’s Syndrome or trisomy 21 is due to an extra 21 chromosome in the fertilized embryo. About 50% of female eggs have defective chromosomes. This increases dramatically as the woman gets older and could be up to 75% by the time she reaches 39.
In an IVF cycle, embryos are pre-screened before implantation, usually through visual screening under the microscope. However, this pre-implantation screening method does not seem to increase IVF success.
Array CGH
Array CGH performs an “inventory” of the chromosomes in the polar body in order to determine whether the egg has the right number of chromosomes. The test takes 1 to 2 days to complete. By pre-screening the eggs before fertilization, only viable, chromosome defect-free embryos are implanted. The chances of success during an IVF procedure are increased two- fold. What is interesting is that the scientists who develop the method reported that healthy, defect-free eggs are not necessary the “best looking” when viewed under the microscope, casting further doubt on visual egg screening.
Strictly speaking, Oliver is not the first baby to be conceived pre-screened. However, other babies born using similar techniques developed from frozen embryos. In Oliver’s case, using the new technique, the egg was screened, fertilized, and implanted within 48 hours, skipping the cryopreservation step.
Oliver’s mom is 41 years old and is of advanced maternal age through no fault of hers. She had three miscarriages and 13 failed IVF attempts. Late last year, the doctors screened 8 of her eggs using, Array CGH and only 2 were found to be normal. One of those eggs was fertilized, implanted and produced Oliver. I remember writing a post about this technique and her story in January when she was still in her 2nd trimester. I’ve been wondering all this time how it worked out and now I’m glad to bring you this update.
The Ethical Issues
As usual, in such cases, there are always ethical issues to deal with. For the pro-life advocates, a human embryo represents life, with or without chromosomal aberrations. Do we have the right to choose? Do we have the right the screen? Is this assisted evolution, favoring the strong over the weak? Others would even venture to criticize: why waste so much time and money on IVF? Why not adopt?
I am pretty sure that for Oliver’s mom, what matters most is that she finally got her wish – her very own baby. After all she’s been through, she must be ecstatic to finally have Oliver, who was born two months ago. Only another mom can understand how she feels.
Oliver is the first but he won’t be the last. With his birth, many wanna-be moms’ hopes have been rekindled. All the best for Oliver and his mom.
Read More
Comment on this blog...