It is more difficult to test twins for a condition like Down’s Syndrome as the results of a blood test cannot be applied to two babies. In this situation, you could either have an amniocentisis later in pregnancy, or you could have the nuchal translucency test.

In this way, your doctor can examine the risks for each baby separately. However, even for the nuchal test, you must take into consideration that a blood test still constitutes part of the overall test and therefore may not be as reliable as it is for one baby, in this respect.

At the nuchal translucency test, the thin layer of fluid (lying between two folds of skin) at the back of the baby’s head is measured. This is because babies with Down’s Syndrome have a thicker layer of fluid in this part of their bodies. Because of the quality of the scan, the sonographer may be able to look for other potential problems such as anencephaly and spina bifida by examining the baby’s brain and spine.
  

On rare occasions, twin babies share a sac of amniotic fluid, but if they have their own sac of amniotic fluid it is possible to take a sample of fluid from each and therefore test both babies.

Obviously testing two babies for a condition like Down’s Syndrome could be problematic, if you were to discover that one of your babies is positive and the other negative. You have to carefully consider what you would do in that situation, as aborting one baby (which is possible) may be especially traumatic for all those involved.

‘Selective termination’, as it is called, is the process by which one twin baby (with a serious abnormality) is aborted, by lethal injection into its heart. There is a small chance that the healthy baby may be affected by the procedure and that both may miscarry and thus may be an extremely difficult decision to make.

Arm yourself with facts when considering this sort of procedure and make sure you understand fully all aspects by talking through your concerns and feelings with an appropriate medical professional beforehand.  

If you would like to talk to other mums about antenatal testing for twins, you can do this on the Tests and Checks or Mum Health area of the chat forum.

Last Modified: 21/06/2007