The British Fertility Society has issued new guidelines, published in the journal Human Fertility, for the use of preimplantation genetic screening (PGS) in patients seeking fertility treatment.  These guidelines follow a thorough review of published research on the safety and success rates of PGS.  PGS involves testing cells from early embryos to detect chromosome abnormalities.  This technique has previously been suggested to increase success rates for IVF in women aged over 35, or those who have suffered repeated IVF failure or recurrent miscarriage.  The British Fertility Society is committed to promoting good clinical practice and working with patients to provide safe and effective fertility treatment.

To summarise, the guidelines state:

  • Current evidence indicates that PGS does not improve pregnancy rates or decrease miscarriage rates for women over the age of 35.  Clinical trials carried out to date show that live birth rates may be significantly reduced following PGS treatment.
  • To date, there have been no robustly designed clinical trials assessing whether PGS is an effective treatment for women who have a history of recurrent miscarriage.
  • It remains possible that PGS may be of benefit under certain circumstances, for example where the number of embryos replaced is strictly limited.  However there is no evidence to support this at the moment.
  • The BFS advises that PGS should preferably only be offered to patients within the context of a robustly designed clinical trial, carried out in a suitably experienced centre.
  • Clinicians should inform their patients that there is no evidence that PGS for advanced maternal age improves their likelihood of becoming pregnant and in some cases may result in a reduced chance of pregnancy.
  • The BFS urgently calls for further research to be carried out on PGS to assess its safety and efficiency in treating a range of patients including those who have suffered repeated miscarriage or implantation failure.

Prof Richard Anderson, author of the guidelines and member of the British Fertility Society’s Policy and Practice Committee, said:

The British Fertility Society wants to ensure that all women receive the safest and most effective treatment when undergoing fertility procedures.  Following a thorough analysis of published research, it is clear that there is currently no compelling evidence that PGS improves the clinical pregnancy rate or live birthrate or that it reduces the miscarriage rate.  Therefore, the British Fertility Society recommends that PGS should preferably only be offered to patients within the context of robustly designed randomised trials performed in experienced centres.  Additionally, patients should be clearly advised that there is currently no evidence that PGS will improve their chances of becoming pregnant.  There is now an urgent need for further research on PGS to assess both its safety and efficiency in treating a range of patients.”

General information

Preimplantation genetic screening assesses whether an embryo (produced by IVF) has the correct number of chromosomes in each cell, prior to reimplantation into the womb.  To achieve this, one cell is removed from an eight-cell embryo and the eight chromosomes that malfunction most frequently are tested.  Only embryos with the correct number of chromosomes are subsequently implanted back into the womb.  The ability to select only chromosomally normal embryos has been suggested to increase success rates for IVF in women aged over 35, those who have several previously unsuccessful IVF cycles, and for couples who have had several miscarriages.  In the UK, this treatment is only licensed for use on patients who meet these criteria.

Please note, this treatment differs from preimplantation genetic diagnosis (PGD), which is a specific test offered to patients who are at a high risk of transmitting a known genetic disorder to their child.

Notes
Abstract
The current status of pre-implantation genetic screening: British Fertility Society Policy and Practice Guidelines

Richard A Anderson1 & Sue Pickering2 for the Policy & Practice Committee of the BFS

1Division of Reproductive and Developmental Science, Centre for Reproductive Biology, University of Edinburgh, Edinburgh, UK and
2
Edinburgh Fertility and Reproductive Endocrine Centre, Royal Infirmary of Edinburgh, Edinburgh, UK.

Preimplantation genetic screening (PGS) has been proposed as a method to improve the success rates of assisted conception in certain indications. Most commonly the technique involves analysing part of the karyotype of one or two biopsied blastomeres by fluorescence in situ hybridisation and thus detecting aneuploid embryos which are then not transferred into the uterus. Proposed indications include advanced maternal age, repeated IVF failure and recurrent miscarriage. While there are a considerable number of reports of the use of this technique, there are only two randomised controlled trials reported at present, both for the indication of advanced maternal age. Neither show an increase in live birth rate, and indeed the more recent (using a relatively low age cut-off of 35 years) suggests that live birth rate is reduced by the use of PGS. Methodological aspects of both studies are discussed. It remains possible that PGS may be of benefit under certain circumstances. However at present patients should be informed that there is no robust evidence that PGS for advanced maternal age improves live birth rate per cycle started, and PGS should preferably be offered within the context of robustly designed randomised trials performed in suitably experienced centres.