A screening technique for embryos could be the key to helping older women have successful IVF treatment.
CCS – Comprehensive Chromosomal Screening – examines the number of chromosomes an embryo has when it reaches blastocyst stage. Genetically normal embryos have 46 chromosomes, 23 from each parent.
Typically, embryos are normally only chosen for transfer by examining them under a microscope, but by studying cells via CCS at blastocyst stage – where an embryo is allowed to develop for longer - it ensures that only those embryos which have the right number of chromosomes are transferred into the uterus.
In the small-scale study carried out in the USA, a group of 60 women who were all aged between 38 and 42 underwent a controlled trial of the new technique versus standard IVF methods of embryo selection.
In the group where CCS was carried out, pregnancy rates went from 33 to 61 per cent – almost double. None of the 30 women whose embryos had undergone CCS miscarried within the first 12 weeks, compared to six women whose embryos were selected via traditional methods.
Importantly, each of the women whose embryos underwent CCS did not have embryo transfer straight away. Each of the embryos which were viable, as identified by the screening, were frozen for a couple of months and then thawed out before transfer, to allow the woman’s body and hormone levels to recover after the necessary drugs and egg collection involved in IVF.
Although this study is only very small scale, it’s a promising sign that IVF success rates are on their way to improving for older women.
Embryos which have chromosome number errors cause various conditions and can often result in early miscarriage, and as women age this risk increases simply because the quality of her eggs is rapidly declining - and therefore so is the quality of any resulting embryos from those eggs. Some studies have shown that by the age of 40, 75 per cent of a woman’s embryos are typically abnormal.
So if only the remaining good embryos can be identified via CCS and used for IVF, then the chances of a successful pregnancy via fertility treatment will improve. We now need to see the results of large scale trials including the impact of CCS on live birth rates.
Last updated: 1st November 2012