The Globe & Mail just published an article about new ways to improve reproductive health entitled “Biological clock running out? Take heart” by Tralee Pearce, from Monday’s Nov 5th – L4 or “Over 40 and trying to conceive? New techniques offer hope” on Sunday’s edition. The article provides interesting insights how to improve the probability of birth after ‘In Vitro Fertilization’ (IVF) with a simple combination of genetic testing and delayed implantation – the method resulted almost a 46% increase in the implantation efficiency. Transfer of fresh embryos without genetic screening led to 38.7% of successful implantations in a group of 38-42 years old, while delayed implantation of genetically pre-screened embryos yielded 56.7% of successful implantations.
One of the important aspects in success of IVF treatment is woman’s health, which is a composite of multiple factors as age, body mass index, history of spontaneous abortions. Partner’s age and fertility status are also determining the success of fertility treatment. Stanford researchers developed predictive model (named PreIVF) that includes the aforementioned parameters as well as the number of previous IVF cycles, woman’s hormone levels, thickness of uterus wall, and many others to show the expected chances of life birth after the IVF treatment.
Luckily, the newly published method can push the success rate even higher than suggested by the PreIVF model as it has a two-prong benefit. Firstly, by freezing embryos and postponing the implantation gives woman the time to recover from the hormonal treatments thus increasing chance for successful implantation. But more importantly the success of this method depends on the pre-implantation genetic screening or preimplantation genetic diagnostics (PGD), which helps to detect embryos with genetic abnormalities that will eventually lead to failed pregnancy or births of a child with genetic disease. Implantation of only a few selected healthy embryos for greatly reduces the risk of multiplex pregnancies, which that typically result in delivery of severely premature babies that in turn has a long-term negative effect on children’s development. Of note- please be mindful when you are reading Wikipedia on PGD, as some of the claims there about negative impact of preimplantation genetic diagnostics on life birth rate are not accurate – the procedure is technically complex and the success rates vary drastically depending on the laboratory!
Very few IVF clinics do offer the preimplantation genetic testing because of high technical complexity and added costs – the genetic testing typically runs over $1,500 for genetic testing. The genetic screening probably is not necessary for relatively young couples that have “mechanical” causes of infertility – i.e. acquired blockage of oviducts or seminal ducts. However, in most cases infertility is a result of weakened reproductive capacity due to a hormonal dysfunction or congenital genetic defects. In the latter case the success of IVF treatment is greatly dependent on the genetic health of the embryos.
It is a very well established fact that with age the number of new spontaneous genetic mutations (de novo mutations) increases for both women and men – so the proportions of defective oocytes and sperm increases with age. Therefore, the larger number of embryos fail to develop properly leading to spontaneous abortions. Spontaneous abortions are the result of severe defects in embryonic development process that is determined by multiple genetic factors. Each failed pregnancy reduces women’s reproductive health, therefore any treatment or other methods that can reduce the risk of a failed pregnancy have significant positive impact.
Pre-implantation genetic screening is a powerful tool essential for improving the efficiency of IVF and ultimately child’s health. However, couples seeking fertility treatments have to think about comprehensive genetic testing well before trying IVF. Genetic testing is commonly done for couples with fertility issues, but this testing is fairly limited and includes only a few genes known to lead to male infertility and analysis of DNA for gross chromosomal abnormalities. Such testing is practically the same as looking for the lost keys under a lamppost and it is inadequate to ensure birth of healthy children.
More comprehensive genetic screening that includes all genes can potentially identify additional genetic abnormalities that underlie the infertility and can have substantial implications for children’s health starting from disease carrier status for common genetic developmental disorders such as cleft palate, which could be also tested at PGD. The same analysis can identify other genetic variations such as carrier status for Cystic Fibrosis, Tay-Sachs, and many other common diseases that do not cause a disease, but may have important health implications for both patents and their kids. For example many of Hypertrophic Cardiomyopathy cases are undiagnosed in general population until first manifestation of disease, which in the case of HCM is sudden death.
Because PGD is expensive in some countries genetic screening of parents is a mandatory requirement. This approach allows more focused analysis of embryos only for couples that have substantially increased risks for severe genetic disorders, while sparing the trouble for couples with low risks.
Furthermore, women seeking donor sperm should be careful when looking for donors as most sperm banks do not conduct genetic screening and rely only on self-reported family history of disease, which is unreliable and cannot determine donor’s carrier status even very common diseases such as Cystic Fibrosis. Therefore, even before seeking a donor women should analyze their own genome to be aware what potential diseases she carries. This knowledge will help to find a donor that is a good match on genetic level.
Genome analysis is a very powerful tool, but still underutilized due to relatively high costs and complexity. Nevertheless, couples should be concerned about the health of their progeny – having healthy children is priceless.
PS: two new publications from New England Journal of Medicine that advocates the use of newer microarray technology for prenatal diagnostics, and for the causative analysis of still birth. This technology is indeed superior to older methods, but this is largely re-active type of diagnostics that missed the intervention opportunity at the pre-implanatation stage. More impertinently, it is much more effective to test the patents before undergoing IVF, in order to determine which risk factors could undermine their fertility and pose risk for fetus development.