Pre-implantation Genetic Diagnosis (PGD) is a technique whereby fertilized embryos can be tested for specific genetic conditions prior to being implanted within the mother's womb.

PGD involves using in-vitro fertilization (IVF), a process frequently used by infertile couples to improve their chances of conceiving a pregnancy. The prospective mother's egg is fertilized outside the body using sperm from the prospective father. Fertilized eggs hopefully become embryos. They are then cultured in the laboratory to the eight-cell stage (three days). One (or more) of the cells from the embryo is then removed (embryo biopsy) and tested for the genetic condition in question. Only those embryos unaffected by the condition and which appear to be growing well are implanted back into the mother.

PGD is an additional option for couples where one or both partners carry a gene mutation for a serious genetic condition that may affect their children. PGD may allow them to have a family free of that particular condition. It has the advantage of allowing the couple to have their own biological children while potentially avoiding termination of an affected pregnancy.

In New Zealand ethical approval has been received for provision of PGD under specific circumstances. Couples where one partner carries an expanded HD gene mutation are eligible for PGD. Other conditions that are approved for PGD include cystic fibrosis, beta- thalassaemia and spinocerebellar ataxia and myotonic dystrophy. The government has announced limited funding for PGD but issues of eligibility and access are still being considered. It is hoped that by the end of 2006 the first couples will be receiving government funded PGD. However, there is likely to be a waiting list.

Privately funded PGD is being performed in New Zealand. The cost is approximately $15 000 for a single cycle (attempt at pregnancy) and is accessed through private fertility clinics. At the time of writing only Fertility Associates in Auckland are providing embryo biopsy, although other clinics are likely to offer this in the future. Due to the limited availability of procedures a couple may need to travel to complete the PGD process.

For example a couple may have egg stimulation, blood tests and monitoring scans at home, then travel to Auckland where the embryos are allowed to grow for approximately three days. The embryos are then biopsied and cells sent to Australia (without their parents!) for genetic testing. Fertility Associates are then advised of the test results and the best choice of embryo is transferred into the mother approximately two days after the biopsy was performed, when the embryo is at the five day stage. This is termed transport PGD.

Despite this, PGD technology has been the preferred choice for many families who wish to avoid a genetic condition in their children.

For more information you may wish to view the "Guidelines for Pre-implantation Genetic Diagnosis" available from the NECAHR (National Ethics Committee on assisted Human Reproduction) website (www.newhealth.govt.nz). Sydney IVF has an excellent website outlining information about PGD.

If you want to get the ball rolling, you can ask your GP for a referral to your nearest genetic service, or fertility clinic.