Amniocentesis: risks, what to expect and should I have one?

Expert advice, risk numbers plus shared experiences from mums who’ve been offered an amniocentesis - to help you make your own decision

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Finding out that your unborn baby may be at a higher risk of having Down’s Syndrome or another genetic disorder can be a confusing and worrying time. You’re thrown into an emotional rollercoaster and at the same time confronted with numbers, risks and probabilities. And then amidst all this, you’re asked to make a huge decision… should I have an amniocentesis?

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While your midwife or consultant will be able to answer your questions about the test itself and the potential outcomes, you might also need additional emotional support and answers to more detailed questions. You’ll also probably want to know exactly what’s going to happen – from an expectant mum’s point of view, rather than just a medical position.

We’ve collected together a range of experiences from MFM mums as well as an expert view, to provide support, guidance and reassurance, to help you make this very personal decision

What is an amniocentesis?

An amniocentesis is a method to take a sample of your baby’s amniotic fluid using a long needle. It’s used to detect health conditions including Down’s, Patau’s and Edwards syndromes, and also cystic fibrosis, muscular dystrophy, sickle cell anaemia and thalassaemia.

An amnio may also be offered to test for neural tube defects, such as spina bifida.

Why have I been offered an amniocentesis?

You’ve most likely been offered an amniocentesis test because an antenatal sceening test has shown a higher than normal risk of your baby having a genetic or chromosomal condition. This could be the result of your combined screening test or the result of a newer test, called NIPT.

The thing to remember is that these results are screening tests, which measure an estimation of risk. It doesn’t mean that your baby does have a genetic condition.

If you’ve had a positive result for Down’s, Edwards’ or Patau’s from a NIPT test, then, because this new test is very accurate, it’s very likely your baby will be affected.

However, if your result is from a combined screen test, for most people the level of risk prompting an amnio is still incredibly low. Don’t be unnerved if you hear it described as ‘High risk’. High risk may mean less than 1% likelihood – more of that below…

So, I’ve been given a risk number, what does this actually mean?

It’s likely that you may be offered an amniocentesis if your combined screening test has shown the risk of a chromosomal or genetic condition to be up to 1 in 150 or possibly up to 1 in 200 in some cases (your age and medical history will play a part).

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These numbers may sound big but they’re not particularly easy to interpret. If you’re given a risk of 1 in 150, then this is saying that out of 150 babies with similar level of risk, 1 baby is likely to have this condition. So 149 are likely not to. Suddenly the risk sounds different.

Another way of looking at it is to change the risk number to a percentage. 1 in 150 risk means your baby has only a 0.67% risk of having a condition – which adds some perspective.

“When my risk score came back with a much higher risk than I was expecting I worried myself silly,” explains MFMer mowani. “I talked it over with hubby who is a maths whiz and he explained what the scores actually mean. 1 in 160 sounds frightening but it is actually the same as a 99.375% chance your baby will not have Down’s.”

Here’s a quick way to turn a 1 in x risk into a percentage:

  • 1 in x risk
  • Divide 1 by x and multiply by 100
  • For example, if you’re given a 1 in 137 risk:
  • Divide 1 by 137 = 0.0073
  • Multiply 0.0073 by 100 = 0.73

The percentage risk is 0.73%. So the estimated likelihood of your baby not having the condition is 99.27%

annbaan says, “I have recently had nuchal test results back that give me a 1.5% chance my baby will have Down’s Syndrome. I’m having an amnio test at 16 weeks to find out for sure. 1.5% does sound like a small chance but is deemed a high risk!”

High risk sounds, well, high. And yet there can’t be too many examples in the world where 1.5% is categorised as High risk.

Talking of risk, is there a risk of miscarriage if I have an amniocentesis?

Yes, there is a risk. It’s not known exactly why the test can bring on a miscarriage, the NHS suggests that it may be down to infection, bleeding or damage to the amniotic sac.

There’s also a very small risk of the placenta being punctured by the needle (this usually heals successfully) or, in 1 in 1000 tests, the risk of a serious infection following the procedure.

According to the NHS, if you have an amnio after 15 weeks of pregnancy, the chance of miscarriage is around 1 in 100 or 1%. (It’s slightly higher if you have an amnio before 15 weeks).

However, this is just an estimation, and there’s no direct evidence that some of these miscarriages may not have happened anyway, without the amnio.

What you can do is ask the hospital what their amniocentesis record is, to give you a better idea.

Mum Haylor explains how she found out her hospital’s past history with amniocentesis. “I was shaking like a leaf when I had to sign the consent forms and go into the room where it was to be performed.

“At this point they had to spell out the fact that there is a risk of miscarriage, and I could call off the procedure at any point if I was not sure. They also stated that it was 17 years ago since they last had a lady at my hospital miscarry after having an amnio.”

Also, the 1 in 100 figure may be higher than the risk you’ve been given for your baby having a genetic condition. So you need to weigh everything up and decide what feels right for you.

“I had an amniocentesis at around 16 weeks. I think my risk was 1:157,” explains MFMer N222. “It was a difficult decision to make but we felt that we had to know, so once the results came in it was almost a foregone conclusion to go ahead with the procedure.

“I had an amniocentesis as I was High Risk (1 in 60) of having a Baby with Down’s Syndrome. I found out on the Monday and was in hospital the next morning to have it done,” says Little_Buggaroo.

Think about what you would do if the result came out positive. Would it make a difference? Remember, there’s no right answer, just a decision that feels right for you and your family.

“I’ve been offered amniocentesis tests for both my boys – turned them down,” shares mummabear. “Wanted a baby, whatever.”

And linz0209 had a similar response. “I refused based on the risk of miscarriage. I know it’s only small but having lost a baby at 25 weeks, I could not cope if the worst did happen. Plus it changed nothing for me. I would not abort, I would continue regardless.”

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So, you can say no to having an amniocentesis?

Yes, the ultimate decision lies with you.

“It is absolutely and categorically a woman’s personal decision whether to have amnio,” explains Jane Fisher from ARC (Antenatal Results and Choices), an independent charity that supports parents through antenatal testing.

“in our experience, medical teams are very non-directive about it because they recognise that because it does carry a small – but always significant – risk of miscarriage, it has to be the woman’s decision.

“Think about how you feel about Down’s Syndrome, or other conditions, and having a child with it,” Jane continues. “How important is it for you to know your child might have Down’s syndrome before they are born?

“This can help you prepare for and adjust to a different scenario than you were expecting with your pregnancy. Or it could help you make other choices, including deciding whether to end your pregnancy depending on your test results.”

Are there any alternatives to amniocentesis?

NIPT – This is a newish blood test for Down’s Syndrome, Edwards’ and Patau’s. It’s starting to be rolled out in some NHS hospitals and is also available privately. Two things to note:

  • NIPT doesn’t have the small miscarriage risk associated with amniocentesis or CVS (chorionic villus sampling)
  • it’s a screening test rather than a diagnostic one, which means it gives you a risk estimate rather than a yes/no result. However, the accuracy of NIPT is very high, and you’ll get a much clearer risk figure than from a combined test

The NIPT isn’t a replacement for amnio or CVS, but can be done from around the 10th week of pregnancy. As it’s a more accurate test than the routine combined screening test, it’s a safer next step after a screening test has indicated a risk of up to 1 in 150. It means you can get a clearer view of the risk before opting for an amnio or CVS.

CVS – The CVS is a process where a sample is taken from the placenta with a needle, usually through the tummy. It’s performed earlier than an amnio, usually between 11 and 14 weeks.

Amniocentesis or CVS – which is safer?

Generally, the amniocentesis and CVS (Chorionic Villus Sampling) are carried out at different times. Amnios are usually done after 15 weeks, whereas CVS tests are usually carried out between 11 to 14 weeks of pregnancy.

Amniocentesis and CVS do have slightly different risks and outcomes:

Risk of miscarriage

  • Amniocentesis – approx 1%
  • CVS – approx 1-2%

Accuracy

  • Amniocentesis – around 98-99% accuracy
  • CVS – around 99% accuracy

If I go ahead, when is an amniocentesis test carried out?

The amnio is usually carried out during 15-20 weeks of your pregnancy. It can be done earlier than this, but this increases the risk of miscarriage or other complications. If it’s advised for you to have a diagnostic test before 15 weeks, you may be offered a CVS.

If you’re already 15 weeks or more pregnant, the amnio can be booked in very quickly; often within a few days but sometimes the very next morning or even on the same day.

While this lessens the time spent worrying, it can also feel like a lot of pressure as there’s not much time to absorb the shock, research your options, and discuss what you want to do.

“At ARC we encourage women to talk everything through,” says Jane. “And because we are independent and not connected to the woman’s hospital or family or partner, they can come to us and ask or say anything. We are here as a resource if you need it.”

What happens if I can’t agree with my partner?

“The two parents should be talking about this and sharing how they feel,” Jane says. “But ultimately it is the woman’s decision as obviously she undergoes the procedure.

“The best scenario is of course one where the couple are at one about what they want to do. And most partners will say ‘it’s your decision and I’ll support you whatever’.”

MFM mum Anxious_Mumma speaks very candidly about how she and her partner made their decision. “We spoke about Down’s Syndrome and what it would mean for us. I had always said ‘We would still keep the baby wouldn’t we? Just because it’s not perfect…’ But I couldn’t sleep that night, I cried, I wallowed in self pity. Did I really want a baby with Down’s Syndrome? I might resent it and be happy for when the time came to have a ‘normal’ baby. I told my partner I didn’t want a baby with DS, that I wouldn’t be able to cope. He agreed and we discussed having an amniocentesis.”

MissusS had a different experience, where her partner wanted to know, but she didn’t. “Had the amnio which wasn’t nice, but a means to an end and my H needed to know the outcome. I would have done without it if it was a sole decision. I’m glad in the end I did as I knew for sure everything was ‘ok’.”

x-Lorraine-x shares, “It has been a horrible few days but we have decided to have the test (booked for this Wednesday) as we feel that we simply couldn’t cope if our baby had Down’s Syndrome and it wouldn’t be fair on our other 2 children. I am now going out of my mind with worry.”

Of course, many find support from other pregnant women and mums in forums. x-Lorraine-x, quoted above, found the friendly MFM mums a great help.

“OMG – thank you so much for taking the time to give me all the details that I have been searching for! I have been on Google every day but not really found any ‘real life’ experiences so your reply was fantastic. At least I know what will happen on Wed and feel more prepared.”

Forums are great places to come and share your experiences, worries and innermost thoughts and it’s totally anonymous – you just create a screen name. Our MFM forum is an incredibly supportive environment and you’ll find plenty of others who have felt just like you’re feeling now. And remember, you don’t have to post; you can just come and read.

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How is an amniocentesis done? And is it painful?

The test involves using a long, thin needle to take a sample of your amniotic fluid, which is the liquid that is in the amniotic sac around your baby.

This is how an amniocentesis is done:

  • Your doctor will put some gel on your tummy and use an ultrasound scanner to check your baby’s position in the womb and the position of the placenta
  • The area of your skin where the needle will be inserted will be cleaned
  • Using an ultrasound as a guide, the doctor will insert the needle and syringe out a sample of amniotic fluid
  • The needle may sting, but many mums describe the sensation as being much like a blood test or like period pain
  • You might feel pressure when the needle is taken out, and after the test, you may have some cramping or some light spotting of blood

MFM mums share their amniocentesis experiences…

“It’s fairly straight forward,” explains mrsS1258. “They clean your tummy, then use ultrasound to guide the needle in – it is quite uncomfortable but not overly painful and is over within a few minutes. They take a sample of the amniotic fluid from the needle for culturing and that’s about it really. You get the fast results back within about 3 days but the full results can take up to 3 weeks to grow.”

“It was not painful in the slightest but a very strange sensation,” recalls Haylor, “as I was able to feel the needle ‘pop’ through every layer of skin, muscle, uterus, etc, I also went very hot, but that could have just been me and the panic.

“Anyway, the first attempt to draw off fluid resulted in nothing but foam, like Fairy Liquid. Thought they were going to have to reinsert (they’re only allowed to carry it out twice on the same day, if these two attempts are unsuccessful they have to leave a few days before attempting again).

“They decided to try rescrewing the vial back onto the top of the needle and luckily this worked. They had to get 15ml for the sample to be sufficient. It was yellowy rather than clear, which for some reason surprised me, as I always thought you would be able to tell the difference between waters breaking and peeing because of the colour!”

jennieblundellhotmailcom didn’t feel pain, just strangeness. “I found the whole procedure really quite painless and all the staff supportive. When they removed the fluid, I can only say it was a slightly strange sensation nothing painful. Afterwards I felt absolutely fine. I was warned of mild period pain and I did take it easy for 48 hours but didn’t seem to get any symptoms.”

What happens after my amniocentesis? Will I get stomach pains?

There is a ‘recovery period’ of around 24 hours after having an amniocentesis where you are asked to rest. You may get cramping (like period pain) for a few hours or experience some blood spotting.

“The doctor usually says to rest for the remainder of the day and that you should be OK to carry on as normal after that,” says Little_Buggaroo “but I was extremely sore several days after and took time off of work to rest.”

Haylor contacted her antenatal clinic at the hospital two days after having her amnio as she was worried about some pain. “I was unsure about the tummy pain I was having.

“It wasn’t by any means severe and it didn’t feel like period pains or contractions, but at the same time didn’t feel like bruising. I had been warned of both of these, but the pain was uncomfortable and constant.

“So the midwives spoke to the consultant and advised me to go in, have an internal and be scanned. I did… and everything was fine.”

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How soon after the amniocentesis am I at risk of miscarriage?

As we’ve explained, there is a small (1%) chance of a miscarriage if you have an amniocentesis after 15 weeks of pregnancy.

Most miscarriages following an amnio happen within the first 72 hours of the test, but some cases happen later – up to 2 weeks – after the amniocentesis.

However, ARC’s Jane Fisher says that in their experience, “Most miscarriages happen quickly, around 72 hours after the procedure, although hospitals will usually say up to about 2 weeks. Once you have gone past 72 hours, the risks go down.”

When do I get the results?

You’ll normally receive a first set of results from the chromosome test within 3 working days. This will tell you whether a major chromosome issue has been identified, such as Down’s Syndrome. If there are further tests being done for other conditions, you’ll receive the results of these within 2 weeks.

“Your clinician will usually sort out with you before the procedure how you want the results delivered,” explains Jane.

Are the results of an amniocentesis 100% accurate?

No, not quite. Amnios are thought to be around 98-99% accurate, so 1-2% of positive results are likely to be incorrect.

“My friend had an amnio and was told she probably would have a Down’s baby. She geared herself up to expect her baby to have Down’s and she was OK with that decision. When Ben was born, he had no signs of Down’s.” explains Bambinobump.

And if I do get a positive result?

While most women, and also most of the MFM mums who posted in our forums, the results from the amniocentesis turned out to be negative women some women do get a positive result for a genetic disorder. If this happens,  your doctor and midwife will spend time with you advising you on your options.

If you need to talk further, you can get great help and advice from the Down’s Syndrome Association. You can call their helpline on 0333 1212 300.

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