THE world's first IVF (in-vitro fertilisation) baby, Louise Brown, was born in 1978 through the technology developed by Sir Robert Edwards and Dr Patrick Steptoe. However the success rate of IVF was very low then.
Over the years newer technologies have been developed to improve the success rate.
One of the reasons for IVF failure is abnormalities within the embryo due to hereditary/genetic disorders.
Some common hereditary conditions can be detected before the embryo is transferred into a woman's uterus during IVF. The technique to diagnose genetic disorders before implantation of the embryo into the uterus is known as PGD ( Preimplantation genetic diagnosis) while the screening of the embryo prior to implantation is known as PGS (Preimplantation genetic screening).
It is a big decision to consider as you need to manage time, finances and emotions to fulfill your dreams of becoming a parent particularly if there is a family history of hereditary diseases.
Parents who have a gene mutation but do not show any symptoms of the disease are called carriers. If both parents are carriers of a gene mutation for the same disease, the probability for the child to inherit the disease is high.
Through IVF, genetic testing can be carried out on embryos. Abnormal embryos which are affected by genetic diseases will not be transferred into the uterus for implantation.
Embryos that have an abnormal number of chromosomes can cause IVF cycle failure or recurrent miscarriages that may be due to inherited hereditary diseases. Through PGS, only healthy embryos will be transferred into the uterus.
Conditions that can be detected through PGS include Down syndrome, Edwards' syndrome, Patau syndrome and Klinefelter syndrome.
However, the limitation of PGS is that it is not possible to screen for all chromosomal anomalies. Screening will be carried out for commonly occurring chromosomal anomalies or those anomalies with a higher incidence.
PGS is recommended for older mums, those with recurrent miscarriages, repetitive implantation failure in previous IVF cycles and those with severe male factor infertility.
The benefit of PGS is still being debated, since screening is not possible for all genetic conditions known. PGD, on the other hand, can be used to identify about 2,000 known inherited single-gene diseases with a 98 per cent accuracy on whether the embryos have inherited unhealthy genes.
PGD is indicated for couples who are carriers of known single gene disorders or at high risk of transmitting single gene disorders to their offspring.
Some single gene disorders that can be detected through PGD include cystic fibrosis, spinal muscular atrophy and beta thalassemia.
PGD is carried out for a specific, known genetic disorder (usually a single gene disorder) which could be transmissible to the offspring. The parents may be affected by a particular genetic disease, they may be the carriers of a genetic disease or may have a genetically affected child from a previous pregnancy.
PGD is aimed at detecting this known genetic disease in the embryo. If the embryo is found to have the genetic disease in question, it will not be transferred into the uterus. Only healthy embryo(s) free of the genetic disease will be transferred into the uterus.
One must remember that PGD requires IVF for fertile couples, who otherwise have no infertility issue. The sole reason for IVF for these couples is to create the embryo by artificial fertilisation so that such an embryo can be subjected to genetic testing prior to transfer back into the uterus.
The genetic disease for which the embryo is tested must be clearly defined.
This way, potential transmission of a known genetic disease to the offspring is avoided.
The advantage of PGD is that, since it requires IVF, multiple embryos can be created during the IVF cycle and genetic testing can be carried out on multiple embryos. The best quality embryo can be chosen and transferred. Transfer of a good quality embryo increases the success rate of IVF.
Since both PGS/PGD require IVF, the financial cost will be a major issue. The cost of PGS/PGD will further add to the cost of IVF and has to be carefully considered.
It is common practice for couples considering PGS/PGD to receive extensive counselling on the indication, financial cost, risk of the procedures and limitations on what could be achieved by these procedures.
*The writer is an obstetrics and gynaecology consultant and fertility specialist at Metro IVF.