Molecular aneuploidy screening of miscarriages:

Conventional chromosome testing (karyotyping) of miscarriage material relies on culture of viable tissue from spontaneous abortions. Although 50-60% of miscarriages are caused by chromosome abnormalities (aneuploidy) it can take several weeks to obtain a result due to extended cell culture. Cell culture facilitates growth of maternal tissue and can give rise to a result that represents the mother rather than the failed pregnancy. And if the miscarriage tissue is not viable, then culture failure will occur without a result obtainable.

Molecular aneuploidy screening by MLPA

Molecular aneuploidy screening can be performed on extracted DNA for a limited number of chromosomes by FastDNA. However, our new and improved aneuploidy screening test, multiplex ligation-dependent probe amplication (MLPA), can screen all 24 chromosomes: e.g. 1 - 22, X and Y.

Essentially, MLPA determines chromosome aneuploidy (trisomies and monosomies) by comparing the number of  copies of chromosome regions in a DNA sample to a normal reference DNA sample.

In a normal sample we have 2 copies of a chromosome (or genes) so we have a chromosome copy number ratio of 2:2, or 1.0 (Figure 1). For trisomy we have 3 copies of a chromosome so there is a copy number ratio of 3:2, or 1.5. For monosomy (1 chromosome copy) we have a a ratio of 1:2, or 0.5. See figure 2 for representative example of chromosome abnormality.

Figure 1: Normal male (test) sample vs Female Reference sample.

Figure 2: Female trisomy 16 sample vs Female Reference sample.

 Figure 3: Monosomy X (45,X) sample vs Female Reference sample.

The advantages of our new MLPA test include avoiding cell culture such that a result can be obtained from non-viable tissue, there is a lower chance of the result reflecting the mother rather than the pregancy and test results are quicker.

For more information on this test, see Molecular Aneuploidy screening: MLPA