Pregnant women are now faced with a baffling number of tests to determine the health of their babies. Is it time for them to just say no?

When Laura Laidlaw became pregnant with her third child, she knew what she wanted in the way of ante-natal testing: nothing. However, as a woman who was now in the over-35 age category, Laidlaw's choice is, for many, neither expected nor straightforward. "I knew from the outset that I just wasn't willing to start on that whole list of tests," she says. "I didn't want an AFP, or a nuchal fold scan, or a CVS, or an amnio. I didn't want all the confusion of false positives and false negatives and likelihoods and risk categories - and I didn't see why clicking over into a different age category suddenly changed me."

The list will be familiar to every pregnant woman over the age of 35. From the first booking appointment, mothers-to-be, especially "older" mothers-to-be, face a catalogue of options, a register of terms they will become familiar with as their baby develops.

Initial samples taken at the first clinic will check basic blood count, blood group, iron levels, liver function and suchlike - but, from that point, additional possibilities emerge. Tests are divided into screening and diagnostic options, the second category being much more invasive than the first. At 11 weeks, the fluid at the back of the baby's neck - the nuchal translucency - can be measured by a scan. By combining the mother's age with information from the scan an individual statistical chance of a chromosome abnormality can be given for that particular pregnancy.

The next marker tends to be the triple test, also known as the Leed's test, or Bart's test. A sample of blood is taken usually between 16-18 weeks and a number of substances will be measured; usually a combination of alpha-fetoprotein (AFP), unconjugated oestriol, inhibin-A and free beta human chorionic gonadotrophin. The concentrations of these substances are used together with the mother's age to estimate her chances of having a baby with Down's syndrome. The level of AFP is also used to determine if there is an increased chance of spina bifida or anencephaly.

If women are found to be at greater risk of having a baby with problems, they will be offered further diagnostic testing - CVS or amniocentesis. CVS (chorionic villae sampling) can be performed early (from 11 weeks). A sample of tissue that will form the placenta is taken either through the cervix or through the abdomen. The risk of miscarriage is 1 per cent. If they choose to wait until later in the pregnancy, an amniocentesis at around 16 weeks will usually be offered to all women over 35. A needle is passed through the mother's abdomen into the uterus, under ultrasound guidance, and a sample of amniotic fluid surrounding the baby is withdrawn. The fluid contains substances from the baby which can be tested for certain conditions such as neural tube defects - spina bifida and anencephaly - and cells which can be grown in culture. The cells can be tested for Down's syndrome and other chromosomal and inherited disorders. Results will take about a week if the tests are on the fluid and up to four weeks if the cells need to be grown for chromosome analysis. Again, the miscarriage rate is believed to be about 1 per cent.

The problem women face is that non-invasive tests such as blood test and nuchal fold scans are merely screening tests and offer no conclusive answers. Tests that give hard information are invasive - and therefore, risky.

"All I felt was utter confusion," says Terry Roberts, from Hampshire. "I was pregnant for the first time at 42, and everyone just spoke about tests and problems and risk categories. I honestly never felt that I could relax in my pregnancy. It was all about timing and making decisions and being faced with things I didn't even want to think about. Given that I had experienced three miscarriages before, the idea that I would sign up for an amnio or CVS that could potentially kill my baby was a complete nightmare for me. I also knew that my chances of getting pregnant again were pretty slim. Down's wouldn't be the end of the world, given that there are so many things worse that can't be screened for. I would have still loved her, she would have still been my daughter. I struggled to avoid an amnio - the NHS hospital made me feel I was being negligent - but my beautiful daughter was born perfect, days after my 43rd birthday and I knew I'd got it right."

More women than ever are having babies past the medical watershed of 35. Over the past 20 years, the number of women giving birth in the 35-39 age group has doubled, with the 40-plus cohort increasing even more. But, for many women, the joy of being pregnant is tempered with the medical reality that they are, officially, higher risk.

"Amnio is usually offered pretty much on the basis of age," says Dr Gillian Penney, honorary senior lecturer in obstetrics and gynaecology at the University of Aberdeen. "It remains the definitive test where the age of the mother-to-be alone puts her in a higher risk category. It isn't 35 across the board - in the Grampian region, it's 37 - but 35 is generally seen as a cut-off point where we start to suggest more screening options.

"Informed choice really is the key. Women need to be provided with absolutely first-class information. I admit that it all used to be rather tokenistic, where the box got ticked to say women had been talked through everything, but I believe things are changing."

Once women consent to the first screening tests, they often find themselves drawn in and having to face yet more choices. Helen Meakins endured weeks of anxiety when, expecting her first baby at 36, her blood test showed a higher than average chance of her baby having Down's syndrome. If she hadn't had the test, she never would have considered amniocentesis, but now the pressure was on.

"After much angst, I decided that if it came to it, I would go ahead and have the baby. But by then, once the idea was planted, I couldn't bear not knowing for sure - if I had a Down's baby I wanted to be prepared. So I decided to go ahead with an amnio. If I'd miscarried as a result, I'd never have been able to forgive myself." Happily, Helen's son Milo, now four, was born healthy. "Now I wish I'd refused all tests," she says.

Caitlin Heavey, 44, an active birth teacher from Edinburgh, refused all testing - including scanning - when her second son was born nine years ago. "But it was a difficult time," she says. "I don't think health professionals necessarily take on board just what you're going through when pregnant. I really couldn't retain information at all. They could tell me my options, but unless I also had something to take away and read and someone I could go back to and ask questions, it was all a façade." Add to that the language and cultural problems for many women, and the notion of informed consent becomes a lot muddier.

"I speak to women in my yoga and pregnancy classes who are just completely befuddled," says Heavey. "These are intelligent, articulate women, who have good careers and impressive lives - but they often get processed by the obstetric conveyor-belt in such an impersonal way that decision-making is a nightmare." Laura Laidlaw agrees. "I truly did feel that I would not have known what to do if the tests had shown me to be in an increased risk category. Could I abort at 20 weeks when I had a bump? When I'd felt so much movement? Unless you know what you're going to do in those circumstances, it's perhaps best not to start on the whole process of screening."

Jane Fisher, director of ARC (Ante-Natal Results and Choices) says: "If a woman is facing the choice about whether to start on testing and screening, has she thought what she will do if she is told she is in a high-risk category? If she would never countenance termination, why start the process in the first place? Similarly, if she is told there is a high chance her baby has Down's syndrome, we'll talk about what her understanding of the condition is before she makes her decision. Sometimes women don't ask questions they don't want the answers to - but there are answers out there and there are some paths through the muddle."

Given that women have differing values, it's no surprise that their reactions to screening options vary too. But, according to Mary Newburn, head of policy research at the National Childbirth Trust, theory and practice vary enormously when it comes down to your baby. "We have found that women have felt pressurised into taking certain routes if they say they want no testing past the age of 35, yet it's different for everyone - whether you have a partner to support you, whether the pregnancy was planned, whether you have had miscarriages in the past." She adds: "Pregnancy has become a much more stressful experience because of the focus on screening. Women get caught up in it without realising they've set foot on the escalator. Older mothers need a chance to celebrate what they're doing - maybe it's time to focus on that just as much."; ARC helpline (020-7631 0285)