9 March 2016

Keeping it Simple - Amniocentesis: Yes or No?

So here you are: maybe you have a 'high risk' result from a combined screening test for T18; maybe you've just had your 20-week scan and they've picked up a bunch of anomalies that they suggest mean T18; maybe you've got a positive result from a Harmony or similar non invasive fetal screening test for T18. Either way you are being offered amniocentesis to confirm the diagnosis and you're not sure whether to have it.

  • Consider amniocentesis if you plan to terminate your pregnancy in the event that T18 is confirmed, if you want to get pregnancy and post-birth management plans in place, or if you cannot live with uncertainty.
  • Consider avoiding amniocentesis if you are not prepared to take the risk of miscarriage, if you think a confirmed diagnosis will lead to treatment being denied to your baby at birth, or if you plan to let nature take its course.

How high is the risk of miscarriage from amniocentesis?

0.5 to 1% miscarriage rate is the standard risk quoted. In studies, the risks range from 0.06% to 2.9% of pregnancies.

All we can really say is:
  1. There is a risk of miscarriage, but it is unclear how high. At worst, it is likely to be around 3 in 100  pregnancies (3%). It may be negligible - as low as 6 in 10,000 pregnancies (0.06%).
  2. There is such a wide variation between studies that it makes sense to conclude that there may be big differences between hospitals and between doctors. You can ask for the risk for your hospital and for the doctor performing your amniocentesis, but they may not give them to you. 

Isn't my screening test good enough? If it says I have a high risk of T18, can't I just assume my baby has it?

If you have had a NIFT (Non-Invasive Fetal Test, for example Harmony or MaterniT21), then it is highly likely but not certain that your baby has T18. Some parents will choose to accept this as a positive result, and some doctors will treat this as a positive result equal to a positive result from amnio.

If you have had a positive combined screening test (nuchal and bloods), this does not mean your baby has T18. Even a 1 in 2 risk would mean a 50% chance your baby does not have T18. Few parents or doctors would treat a high-risk combined screening test alone as confirmation of T18. You may choose NIFT to give you a clearer indication, or move onto amnio.

Suspicious ultrasound findings can be very predictive of T18, especially if combined with a high-risk combined screening test result. Some parents and doctors would treat these as a positive, but most would confirm via amnio or opt for a clearer screening test result by using NIFT. 

Doesn't a high-risk screening result mean that I can prepare as if my baby has T18, but my doctors can't deny treatment to my baby at birth as it isn't a certainty?

Yes, possibly. You can choose to assume that your baby has T18 and prepare for that outcome. Most doctors will not deny treatment on the basis of a screening test result alone, so it is less likely they will deny treatment at birth. However some doctors may treat a positive NIFT, especially combined with suspicious ultrasound results, as a confirmation of T18 and deny treatment on that basis. They may or may not be on shaky legal ground by doing so. 

So if I want full treatment for my baby, shouldn't I avoid confirming the diagnosis by amnio?

I would say that a confirmed diagnosis by amnio gives you many advantages in this situation. It means that:
  • You can agree post-birth care plans while you have the time and energy to do so (ie. before your baby arrives).
  • You can ensure that your pregnancy is managed appropriately to minimise the high risk of stillbirth.
  • You can get agreements in place for monitoring in labour and interventions if needed.
  • You can seek other healthcare providers if you can't get agreement from your current providers (after birth you're pretty much stuck).
  • You have time to manage disagreements if you stick to your current providers. You are absolutely stuck if they refuse to ventilate at birth: you have no time to argue, no options at all. If you've argued that point in pregnancy and can't reach agreement, you can escalate. Even go to court if needed and have agreements in place for when your baby is born.

On the other hand, if your providers are unwilling to provide treatment and you have no viable options to transfer to, you are in for a long fight which you may not win. If you are in a remote location with a limited choice of providers this may affect the decision of whether to have an amnio. 

If I want to choose palliative care for my baby, is there any point choosing to confirm by amnio?

I would say yes again. Having a confirmed diagnosis means that:
  • You can access palliative care teams, children's hospices and community nurse teams in pregnancy.
  • You can agree a limited care plan pre-birth, so your baby will not receive invasive treatment you don't want.
  • You can discuss decisions and options regarding where your limits lie, what treatments you will accept and how you will manage your baby. 

I would terminate my pregnancy if T18 is confirmed. Should I have an amnio?

The only way to confirm your baby has T18 is to have an amnio, so yes, I would say in this situation that amnio is your best option. Some parents may choose to terminate on the basis of a positive NIFT, especially if combined with suspicious ultrasound findings, but others would feel that they would always have doubts. An amnio is usually the best option.

The decision about whether to opt for amniocentesis is never easy, but by weighing up all the factors, you will come to the best decision for you and your baby.

For a more detailed look at the question of whether to have an amniocentesis, read the full version of this post.

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