New test to improve IVF success rate

29th June 2010 - The efficacy of preimplantation genetic screening (PGS) has been one of the most hotly disputed subjects in assisted reproduction over the past few years. The European Society of Human Reproduction and Embryology (ESHRE) PGS Task Force has now shown that screening of polar bodies (the tiny part of an egg that contains the egg’s chromosomes but does not take part in the fertilisation process), is a reliable way to analyse the chromosomal status of an egg.

The new screening test can be used to check that eggs don’t have any missing or extra chromosomes, enabling doctors to  determine which of a woman’s eggs are most suitable for fertilisation and implantation. The new test provides results in just 12 hours, meaning it can be used in fresh IVF cycles and avoids the freezing of embryos.
Last autumn a 41-year-old woman with history of miscarriages gave birth to a baby boy, Oliver, after using the new screening method and now ESHRE has shown the test can identify the chromosomal status of eggs in 89 % of all polar bodies analysed.

The makers of the new test, BlueGnome, say they believe it’s more accurate than previous techniques which relied on visual inspection of the embryo under a microscope.  

Correct chromosomes

Many scientists believe that cells with the incorrect number of chromosomes, a condition termed aneuploidy (a type of chromosomal abnormality), are a major cause of infertility and that the identification of such cells has the potential to significantly improve IVF success rates.

Until now however, the technical challenge of reliably counting chromosomes in single cells has made it very difficult to rigorously test this hypothesis.

The new test, called 24sure, is particularly useful for older women, as their eggs are often of lower quality than those from younger patients.

If the polar bodies tested have the correct number of chromosomes, then so does the egg. This improves the chance of implantion in the womb and the creation of a successful pregnancy.

Independent, two centre, clinical study

Scientists at the University of Bonn and at the SISMER centre in Bologna studied the new test. Professor Joep Geraedts told the 26th Annual Meeting of the European Society of Human Reproduction and Embryology in Rome that they were able to identify the chromosomal status of the eggs in 89 % of all polar bodies analysed.

In both centres all eggs from patients that were obtained after ovarian hyperstimulation, egg retrieval and fertilisation were biopsied for polar bodies 1 and 2. In those cases where aneuploidy was predicted, the egg was studied as well to confirm the findings. The Centre for Reproductive Medicine in Amsterdam analysed all data and provided the final results.

The analysis of polar body 1 already detected 72 % of all aneuploid eggs, but adding the analysis of the second polar body significantly improved the detection rate up to 89 %.
“With chromosome errors being the predominant cause of non-viability of the embryo, we hope this approach will in future effectively improve results in assisted reproduction,” said Professor Geraedts, past ESHRE chairman and coordinator of the PGS Task Force in a press release.