Preimplantation genetic testing.
OBJECTIVE
To review the techniques and indications of preimplantation genetic testing, including preimplantation genetic diagnosis and screening.


METHODS
Limited to an introductory discussion about the genetic aspects of preimplantation reproductive techniques.


RESULTS
This update does not discuss in detail the adverse outcomes that have been recorded in association with assisted reproductive technologies.


METHODS
The Cochrane Library and Medline were searched for articles relating to preimplantation testing that were published from 1990 to February 2008, using the following terms: preimplantation genetic diagnosis, preimplantation genetic screening, and in vitro fertilization. Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Additional publications were identified from the bibliographies of these articles. Randomized controlled trials were considered evidence of the highest quality, followed by cohort studies. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and from national and international medical specialty societies.


METHODS
This update is a consensus of the Genetics Committee of the Society of Obstetricians and Gynaecologists of Canada. The recommendations were made according to guidelines developed by the Canadian Task Force on Preventive Health Care.


RESULTS
This update educates readers about new genetic concepts, directions, and technology. The major harms and costs identified are those of assisted reproductive technologies.


BACKGROUND
The Society of Obstetricians and Gynaecologists of Canada.


CONCLUSIONS
Preimplantation genetic diagnosis is an alternative to prenatal diagnosis for the detection of genetic disorders in couples at risk of transmitting a genetic condition to their offspring. Preimplantation genetic screening has been proposed to improve the effectiveness of in vitro fertilization in women of advanced maternal age or in couples with recurrent miscarriage or implantation failure, but the benefits of this approach are debated.


CONCLUSIONS
The recommendations were made according to guidelines developed by the Canadian Task Force on Preventive Health Care. 1. Before preimplantation genetic diagnosis is performed, genetic counselling must be provided to ensure that patients fully understand the risk of having an affected child, the impact of the disease on an affected child, and the benefits and limitations of all available options for preimplantation and prenatal diagnosis. (III-A) 2. Couples should be informed that preimplantation genetic diagnosis can reduce the risk of conceiving a child with a genetic abnormality carried by one or both parents if that abnormality can be identified with tests performed on a single cell. (II-2B) 3. Invasive prenatal testing to confirm the results of preimplantation genetic diagnosis is encouraged because the methods used for preimplantation genetic diagnosis have technical limitations that include the possibility of a false negative result. (II-2B) 4. Before preimplantation genetic screening is performed, thorough education and counselling must be provided to ensure that patients fully understand the limitations of the technique, the risk of error, and the lack of evidence that preimplantation genetic screening improves live-birth rates. (III-A) 5. Available evidence does not support the use of preimplantation genetic screening as currently performed to improve live-birth rates in patients with advanced maternal age, recurrent implantation failure, or recurrent pregnancy loss. (I-D).
Audibert
François
F
The Society of Obstetricians and Gynaecologists of Canada (SOGC), Montreal, QC.
Wilson
R Douglas
RD
Allen
Victoria
V
Blight
Claire
C
Brock
Jo-Ann
JA
Désilets
Valérie Anne
VA
Gagnon
Alain
A
Johnson
Jo-Ann
JA
Langlois
Sylvie
S
Wyatt
Phil
P
D010064:Embryo Implantation; D005260:Female; D005820:Genetic Testing; D006801:Humans; D011247:Pregnancy; D019836:Preimplantation Diagnosis