Chromosome aneuploidy describes the condition in which there is an incorrect number of chromosomes in an embryo. In a normal embryo, there are 22 pairs of chromosomes plus the two sex chromosomes. One of each pair is inherited from our mother and father in the egg and sperm in fertilisation. Most aneuploidies are lethal to the embryo and are a major cause of IVF failure and miscarriage. In rare cases, they result in abnormal pregnancy and an affected child.
The majority of aneuploid embryos (90%) occur when eggs with extra or missing chromosomes are fertilised. Sperm cells may also be aneuploidy but the prevalence is usually lower (around 10%).
How can we detect aneuploidy?
We remove one or more cells from each egg or embryo and examine the number of chromosomes using either aCGH or NGS technology. For most women rates of aneuploidy increase once they reach their mid thirties, and women in their mid-forties struggle to achieve healthy pregnancies for the same reason (see One by One Plus).
Would you benefit from this test?
All women in their late thirties and early forties should consider this option, especially if they have already had unsuccessful IVF treatment or miscarriage.
Aneuploidy screening may improve pregnancy and live birth rates, because only those embryos with normal numbers of balanced chromosomes are selected for transfer. If all embryos are found to be aneuploid, screeing will enable you to make an important decision about embryo transfer and IVF treatment. Egg donation is a possible alternative and one which normally offers much higher success rates. Other couples who may find aneuploidy screening reassuring are those considering elective single blastocyst transfer to avoid the risk of multiple pregnancies. There is now evidence that pregnancy rates are significantly improved by testing for aneuploidy (see One by One Plus).