Prof Phil Steer gives help to older mothers, explaining the risks of pregnancy after 35.
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Anastasia Baker: With many women choosing to have babies later in life, they need to remember that conceiving become steadily more difficult after 35. Their may also have more problems during their pregnancy. Professor Philip Steer is a Consultant Obstetrician of the Chelsea and Westminster Hospital in London. Welcome to you. Prof. Philip Steer: Thank you. Anastasia Baker: So what problems do older women have when they're trying to conceive? Prof. Philip Steer: Well, the main problem is that a woman is born with all the eggs she will ever have. Then when she goes through the menarche and goes to puberty, she will start to ovulate regularly, but is in the limited supply of those eggs. By the time that she reaches 35, her ability to produce the right hormones and so on to ovulate regularly will start to decline. So that by the time a woman is 40, she is going to have about half the chance of getting pregnant that as much she was 20. By the time she is 45, that's down to 1-10%. Anastasia Baker: So is 20 the best age to really conceive the -- young but --? Prof. Philip Steer: Ideally -- yes, in terms of conceiving, 20-30 is probably ideal. In terms of actually carrying the baby, we know that mothers from 30-35 also do very well and moreover they have better skills at looking after the baby after it's born. So probably the ideal age group for having baby is 25-35. Anastasia Baker: So are older women likely to have more abnormal babies then? Prof. Philip Steer: Yes, the biggest problem, once you get above 35, is the increasing risk of having a baby with Down syndrome. This is what we called Trisomy 21. Anastasia Baker: But there are lots of tests out there that can detect Down syndrome. Prof. Philip Steer: Yes, but they are all screening tests. And all of them have a significant false-negative rate. So even with the best test, you're going to pick up about 85% of affected babies. So even with the best screening test, they are still going to be some babies who will be born unexpectedly with Down syndrome. Anastasia Baker: What is a false-negative test? Prof. Philip Steer: A false-negative test is where the test of pH to give you a normal result, but the baby is, in fact, abnormal. Anastasia Baker: Alright, okay. What can you do about that? Prof. Philip Steer: Well, there's nothing really you can do during the pregnancy. What we need to distinguish clearly between a screening test, which is what most women have. So either a scan at 12 weeks, it's called a Nuchal Translucency Screen, or a blood test at about 18 weeks, it's called a Serum Screen or the anomaly scan at around 18-22 weeks which will pick up about half the babies with Down syndrome. These are all screening tests, which means that you can pick up between them, 85-90% of babies with Down syndrome. But some Down syndrome babies look normal on a scan and they are often actually the healthiest than the babies when they're born. So there isn't necessarily a way that you'll be able to pick them up. What you then need to think about doing is a diagnostic test which is actually putting a needle in, taking fluid from around the baby, culturing the cells and actually looking at the chromosomes to see if this child has the normal number of chromosomes or has an extra chromosome making it Down syndrome. This is called the diagnostic test. Now clearly, this is much more reliable in terms of picking the babies up, but unfortunately, about one to a half of percent, that's 1 in 1-200 babies will be lost from the side effect of the test. So unlike screening tests, it's more risky. Anastasia Baker: So why is it 35? Why is that the turning point? Why is that the key age? Prof. Philip Steer: Yeah. It's not actually really 35. The risk of having a Down's baby goes up from the age of about 20 onwards as the eggs get older. So you're born with all the eggs you have and so as you expose it to radiation and background and X-rays and ultraviolet, all sorts of rays -- Anastasia Baker: Other than Dow