Choosing the best embryo is the key to success in IVF
In vitro fertilization (IVF), a technique adopted to give birth when natural methods fail, comes with its own share of problems.
A recent report by researchers at the University of Montreal Hospital Research Centre (CRCHUM) shows that embryos obtained after fertilisation in a test tube are often defective.
“About half of embryos used in fertility treatments have some cells that contain the wrong number of chromosomes. These so-called ‘mosaic’ embryos are considered of poor quality and many clinics choose not to transfer them to the woman,” Greg FitzHarris, a researcher at the CRCHUM and professor at the University of Montreal, said.
Speaking about poor quality embryos, he told Down To Earth, “It is considered that a mosaic embryo is less likely to implant and develop to term. In embryos, it (an abnormal number of chromosomes) can cause (often) failure to develop or (sometimes) developmental disorders. In other cells (not embryos) it can lead to cancer.”
Experimentation with mice
According to FitzHarris, researchers arrived at the conclusion by studying embryos in mice. “Mouse embryos are traditionally/commonly used to study mammalian development. Human embryos are very rarely made available for research, and therefore mouse embryos, which can be harvested easily, are a good alternative.”
In mice, normal oocytes (eggs) contain 20 chromosomes, while in humans they contain 23. Having an abnormal number of chromosomes in cells, known as aneuploidy, is a well-known problem in reproductive biology.
“In eggs and embryos, aneuploidy is usually associated with infertility. However, opinions are divided as intuitively one imagines aneuploid cells must be a bad thing. But at the same time so many embryos are found to be mosaic in the clinic that perhaps this suggests that some of these must ultimately have the ability to become a (normal) baby,” FitzHarris added.
The issue of isolating mosaic embryos is controversial. Some clinicians believe that defective embryos should not be used. Others argue that mosaic embryos can produce healthy children, suggesting that embryos can repair themselves naturally.
Choosing the best embryo is the key to success when it comes to IVF. “…discoveries like this might eventually allow clinics to know the ploidy (number of sets of chromosomes in a cell) status of an embryo without the need for (invasive) biopsy,” FitzHarris said.
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