Preimplantation Genetic Screening and Preimplantation Genetic Diagnosis
The CARE team has developed and introduced many new fertility treatments and technologies over the years. CARE pioneered the Array CGH technology and in 2009 the world's first baby, conceived after Array CGH with IVF, was born following treatment in a CARE clinic. In addition, CARE pioneered the Blastocyst (Trophoblast) Chromosome Screening technology in the UK. We were also one of the first UK clinics to perform Preimplantation Genetic Diagnosis, and the first to be licensed to undertake tissue typing.
Our Genetics Programme incorporates both Preimplantation Genetics Screening and Preimplantation Genetic Diagnosis.
Preimplantation Genetic Screening (PGS)
The most common reason why IVF fails is chromosomal abnormality. Approximately 70% of embryos produced, either through natural conception or IVF, are lost before birth. The vast majority of embryos are lost within the first three months of pregnancy, most of these even before implantation. A major cause of embryo loss, including miscarriage, is a chromosome abnormality (known as 'anueploidy'), where there is either a loss of a chromosome or a gain. A chromosome is a highly complex structure containing genes that make us who we are, and they are found in every cell in our body (except red blood cells). One chromosome may carry over 1,000 genes. Chromosomes are in pairs, and in humans there are 23 pairs. It has been demonstrated that more than 50% of human eggs have a chromosome anomaly. As this increases significantly with age, it is believed to be the main reason why women of advanced reproductive age have such difficulties conceiving and also have a high incidence of miscarriage and fetal abnormalities such as Downs Syndrome.
Embryologists in routine IVF practice cannot differentiate between chromosomally viable and aneuploid eggs/embryos, and hence aneuploid embryos will unwittingly and inevitably be transferred to the womb, thereby compromising IVF outcome. Conversely, it follows that by using screening techniques to identify the aneuploid status of the egg, embryologists have up to 85% chance of eliminating the chromosomally abnormal embryos before transfer.
It is hoped that this should not only lead to markedly improved IVF success rates and reduce the incidence of multiple pregnancies (by transferring fewer but 'competent' embryos) but also reduce the incidence of pregnancy wastage (miscarriage).
Array CGH is suitable for all patients. It is particularly suitable for the following groups: women who are aged over 37; men who have been shown to have sperm at risk of carrying abnormal chromosomes; couples who have had several miscarriages or several attempts at IVF but failed without explanation. But, knowing that even the younger female is at risk of up to half her eggs carrying a chromosome anomaly, it could be argued that using Array CGH to effectively eliminate all such eggs or embryos will increase the chance of success for those couples.
Preimplantation Genetic Diagnosis (PGD)
Preimplantation Genetic Diagnosis is a technology which allows genetic testing of an embryo prior to implantation and before pregnancy occurs. It is used in conjunction with IVF and allows only those embryos diagnosed as being free of a specific genetic disorder to be transferred into a woman to try to achieve a pregnancy.
Our state of the art PGD laboratory at our unit in Nottingham, working in conjunction with the world renowned Genesis Genetics Institute, offers the most advanced technology available to patients. This collaboration provides couples with access to the expertise and skill of both the Genesis Genetics Institute and the CARE Fertility team. Genesis Genetics undertakes more than half the PGD carried out worldwide and their molecular genetics labs service over 250 IVF centres, including every major university in the United States and Canada. Professor Mark Hughes is the President of Genesis Genetics and a pioneer in the field of PGD. Genesis Genetics has tested for many hundreds of genetic conditions, more than any other facility worldwide. With modern technology we can now screen for almost any single gene disorder, and new conditions are being introduced all the time. Within a period of as little as 5-6 weeks a test can be designed for couples with inherited diseases and unique gene mutations.