Fertility experts have stated that couples with family history of genetic abnormality stand a chance to have healthy babies via In Vitro Fertilisation, through a medical procedure known as Pre-implantation Genetic Diagnosis, PGD.
The experts noted that with PGD, an embryo can be screened for abnormalities and unwanted traits such as congenital blindness before being transferred into the uterus (womb), adding that this helps to reduce pregnancy termination and birth with genetic abnormalities.
IVF is an advanced type of assisted reproductive technology that involves retrieving eggs from a woman’s ovaries and fertilising them with sperm.
The fertilised egg, which is known as an embryo, can be frozen for storage or transferred to a woman’s uterus.
According to the National Institute of Health, pre-implantation genetic diagnosis involves testing the early embryo after in vitro fertilization.
It explained that the procedure can be deployed to determine the sex of the embryo for sex linked disorders, identify single gene defects and chromosomal disorders.
Speaking in an interview with PUNCH HealthWise, the Medical Director of Nordica Fertility Centre, Dr. Abayomi Ajayi, said PGD allows for studying of the DNA of eggs or embryos to select those that carry certain mutations for genetic diseases.
He noted that the advanced medical procedure makes it highly likely that a baby will be free of the disease under consideration like congenital blindness, and that it is useful when there are previous chromosomal or genetic disorders in the family.
Dr Ajayi said congenital blindness can be caused by several factors, and that everything is not only about genetic. He said:
“The ones with genes responsible for congenital glaucoma, retinitis pigmentosa and all those things that can cause genetic blindness, that are genetic in origin, can be addressed through pre-implantation genetic diagnosis.
“There’s need to be careful because not every congenital blindness has a genetic reason to it. The ones that the genes have been discovered, IVF will definitely help through genetic testing by looking at the embryos that are free from the affected genes.
“If the abnormality is passed from one generation to the other, it is likely to be genetic, and therefore, they might probably benefit from IVF. That’s the only way IVF can help.
“About 60 per cent of congenital blindness has genetic origin. So, we need to be sure that it is the one that has genetic origin and be that it belongs to that group.”
The fertility specialist explained that the first step to be taken is to diagnosis what has been passed on from one generation to another, adding that once the gene responsible has been identified, normal IVF is carried out and a sample is taken from the embryos and sent to the laboratory to ensure that the abnormal genes are not expressed in the embryos harvested.
He, however, noted that it is not likely that all the embryos will have the abnormal gene.
Recalling an experience with a patient with a history of congenital blindness, Ajayi who is the MD of Nordica Fertility centre, said it was unfortunate the woman had no embryos that could be transferred, as all of them had the gene.
“The client was advised to use donor eggs,” he said, adding “Sometimes, such situation could arise, but it depends on the inheritance of the genes involved and what percentage of the chances are there that if an individual has a particular abnormal gene, the offspring could end up with it.
“These are some of the things that genetic counselling will also help to achieve. So, we do PGD and get a genetic counsellor. But the first is to make the diagnosis and know what is being passed on to start with, and to know if the gene responsible has been identified.
“From there, we can pick it up to say okay, if we do PGD, we probably can sidestep the embryos carrying such genes. Sometimes, if we can’t, it might then be possible to suggest the use of donor eggs for such couples.”
Speaking on how PGD is carried out, a Reproductive Endocrinologist, Dr. Kemi Ailoje, explained that on the fifth or sixth day of development (blastocysts), embryos that are of good quality are selected for the procedure.
“It involves micro-surgically removal of cells, that is, the trophectoderm/blastomeres which are a representative of the embryo.
“These embryos are then cryopreserved (frozen) and the DNA of the cells is then screened for problematic genes present in each embryo.
“Embryos that are free of genetic abnormalities are selected and transferred to the uterus (womb) for possible implantation. Additional embryos of good quality are cryopreserved — frozen — for later use,”
Ailoje, who is the Managing Director of Lifelink Fertility Centre, noted that the process takes about four weeks in a fresh embryo transfer or six to eight weeks, or more in a frozen embryo transfer.
“This involves the endometrial (baby bed) preparation for implantation of embryos,” she added.
In term of cost, the fertility specialist said pre-implantation testing is an advanced technology that requires a lot of specialised laboratory work.
She said the cost implication of the process depends on the number of embryos to be screened and the abnormalities screened for, adding that the cost varies worldwide.
For couples with history of genetic abnormality, who might not afford to pay for embryo screening, Ailoje recommended the option of using screened donor embryos. She said,
“Couples who are at risk of passing a genetic disease to their children can have donor eggs or donor embryos. However, most couples prefer to try IVF using their own embryos that have been genetically tested for inherited disorders.
“If you are using donor eggs, decide whether to use eggs from a friend, family member, or anonymous donor. If you decide to use donor eggs from an anonymous donor, you can find one through a fertility clinic, a frozen egg bank, or an egg donation agency.
“You will usually be able to choose the donor based on physical characteristics, ethnic background, educational record, occupation, among others.
“Most egg donors are between an average age of 21 to 29 years, and would have had medical and genetic screening prior to the process.”