Diet and Health FAQ

Tagged As: Second Trimester Pregnant

Question:
My partner Juliet is 20 weeks pregnant. We learnt last week that the child shows one of the 'soft markers' for chromosomal abnormality - we have been given a 1 in 660 chance of abnormality and offered the choice of an amniocentesis. We are in a quandary. We know that the amnio has an associated chance of miscarriage but it's not clear to us how that risk might vary with the length of the pregnancy. We've been told that the average for the UK (we live in London) is a 1% chance of miscarriage but have also read that the risk declines with time and that first second trimester amnios have lower risk. To try to balance the risks, we'd like to find some numbers on real world risk against length of pregnancy. Any ideas? Any general comments?

Answer:
Just my opinion but why get the amnio at all? If it did show a chromosomal abnormality, would that affect your decision to have a child? A 1 in 660 chance of abnormality is very low. This also means you have 659 chances for no abnormalities. I know this is a very individual issue, but personally I think the risk of miscarriage in your case outweighs the risk of abnormality. I've had an amnio at 24 weeks during which my water broke. There were a lot of other factors (they were checking for bleeding and bacteria, not abnormalities), but still, it happened. During my next pregnancy, our AFP test came back with a 1 in 128 chance for Downs. I still couldn't have another amnio, I was too scared of it. I had a high level ultrasound which was perfect, but of course not the definitive answer. The rest of pregnancy I just had to stay positive and hopeful. Our son turned out not to have Down's (1 yr old already). The figure of 0.5-1% is for amnios at about 18-22 weeks. Many scans performed in the second trimester find the presence of soft markers and when there is only one, these are not usually reported because of uncertainty about the *actual* risk. There is little definitive data for most of them. 1/660 is a low risk, too. If, for example, this was the risk assessment of a Down's serum screening test you would not be advised amniocentesis. On a personal level, I wouldn't want amnio at this level of risk, but you've got to be happy with your decision, so you can deal with the outcome, whatever it may be.