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Genetic screening of embryos makes no difference to births

13 August 2018
Appeared in BioNews 962

Preimplantation genetic testing of embryos does not improve IVF birth rates in older women, found the largest study of its kind yet.

Professor Karen Sermon at the Vrije Univeriteit in Brussels, Belgium, who led the study, said she 'saw no benefit' in using the controversial technique (see BioNews 930) which assesses chromosomal abnormalities to help select for embryos for implantation in IVF.

The randomised controlled trial followed 396 women aged 36 to 40 years undergoing treatment at fertility centres in seven countries from 2012. About half the patients received PGT-A (pre-implantation genetic testing for aneuploidy) prior to embryo implantation, while the other half received IVF only.

After one year and the first cycle of IVF, the percentage of women from both groups who had had a baby was identical at 24 percent.

The second endpoint of the study looked at the rate of miscarriages and embryo transfers and found that with PGT-A both were significantly reduced, with miscarriages decreasing from 14 percent in the IVF only group, to 7 percent in the PGT-A group.

The researchers note that the results indicate a possible greater efficiency of transfers with PGT-A, but caution that it has yet to be seen whether these benefits outweigh the cost and invasiveness of the procedure.

'All too often couples requiring IVF treatment are taken for a ride when it comes to a bewildering array of unproven tests and adjuvant treatments,' said Professor Jan Brosens at the University of Warwick in the UK, who was not involved in the study.

'Patients need to be empowered to make choices based on clinical evidence. This smartly designed and well conducted study was designed to give couples clear-cut information on whether PGT-A increases the chance of having a baby within one year. The answer is no.'

He added: 'Yet the finding that PGT-A reduces the number of procedures and decreases the risk of miscarriage may sway some couples to opt for this intervention.'

Some experts however caution that the decreased miscarriage rate seen might not be clear cut.

'The authors stated that as a result of PGT, there were less embryo transfers and a lower miscarriage rate, and many IVF clinics may well erroneously seize this as a "selling point" for PGT-A,' said Professor Ying Cheong at the University of Southampton, and clinical director of Complete Fertility in Southampton. 'It needs to be emphasised that these are secondary end-points which the study was not powered to definitively answer and so must be interpreted with caution.'

While the study has been praised by many experts for its design, many have also pointed to a major limitation: namely that the genetic screening method used is not one that is commonly used now.

The PGT-A in the study analysed the polar bodies – non-functional cells ejected by the egg prior to its first division after fertilisation (see BioNews 581). When the study started recruiting patients in 2012 this was a state-of-the-art technique. Using polar bodies to analyse the maternal chromosomes was seen as less invasive than taking cells from the actual embryo. However, the technique has since been replaced by the harvesting of genetic material from the blastocyst five days after fertilisation as methods of genetic analysis have improved.

The study was published in the journal Human Reproduction.

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