I’ve been refreshing my pre-eclampsia knowledge because two new screening tests came out for it in May.
They're recommended by NICE guidelines and I'm fascinated. I'll get onto all the ins and outs in this post but first, pre-eclampsia...
Pregnancy is a challenge for the immune system because two genetically different beings have to co-exist.
Pre-eclampsia is a condition which occurs when the immune system doesn’t get things quite right.
It's characterised by high blood pressure, which can cause swelling and headaches, and protein in the urine and can progress to fitting and death (see more on signs and symptoms here.)
It’s helpful to visualise what’s causing it. Research suggests there are two main parts to pre-eclampsia:
One: The placenta implants shallowly – it's kind of not ‘plumbed in’ correctly.
We think this is because of a complicated immune response between fetal and maternal cells when the placenta implants. The excitingly named ‘Natural Killer’ cells in the uterus, and the ‘Major Histocompatibility Complex’ cells from the fetus are supposed to mesh better than they do.
The blood vessels of the placenta don't develop correctly and don't go deep enough.
Two: The fetus doesn’t get enough oxygen or nutrients so ‘distress signal’ molecules are sent out into Mum’s immune system.
Babies can suffer from intrauterine growth restriction and need to be delivered early because the placenta isn't working as well as it should. The condition of pre-eclampsia can get worse because of the immune response.
It’s horrible and can occur in healthy women.
The two new blood tests available for pre-eclampsia sound complicated.
When I looked up the NICE guidelines and saw the title was: ‘Triage PlGF test, Elecsys immunoassay sFlt-1/PlGF ratio, DELFIA Xpress PlGF 1-2-3 test and BRAHMS sFlt-1 Kryptor/BRAHMS PlGF plus Kryptor PE ratio.’
My face went :/
But though researchers should cover the tasteful and understandable creation of acronyms as part of their education, the tests are actually simple.
Get past the big words and you can see that NICE recommends the:
Immunoassay SFlt-PIGF ratio
Stay with me, I promise you’ll pick this up fast.
Placental Growth Factor and Soluble fms-like tyrosine Kinase-1, or PIGF and SFlt, as they’re known to friends, help regulate the implantation and growth of the placenta.
PIGF is one of the things that helps new blood vessels grow and SFlt is one of the proteins that inhibits blood vessel growth.
In a healthy pregnancy, the two do a delicate dance to make sure mum and baby are healthy.
In women with pre-eclampsia, there are problems with the placenta implanting, so PIGF levels are lower and SFlt levels are higher than normal.
The PIGF test looks at the amount of Placental Growth Factor.
The Immunoassay SFlt-PIGF test looks at both factors and gives a helpful ratio.
Research suggests the two tests together are useful in the diagnosis and management of pre-eclampsia.
So far, so good. As the Royal College of Midwives says; 'we welcome any test that can predict or screen for pre-eclampsia', right?
Like all screening tests, there are significant ethics to consider.
The Bad Stuff About The Tests:
These are screening rather than diagnostic tests.
We’re all familiar with diagnostic tests – for instance, an x-ray will show whether you have a broken leg or not.
But a screening test doesn’t give a ‘yes’ or ‘no’, it gives a degree of probability.
Ending up with a negative result from these tests means midwives can reassure women they’re not likely to have pre-eclampsia (at least right then). In the case of a woman with blood pressure creeping up and some protein in
her urine, which happens sometimes in pregnancy for reasons unrelated to pre-eclampsia, it could be a godsend.
However, the tests are only good at predicting what will happen in the short-term.
The test being negative and reassuring only predicts what will happen within the next 7-14 days, which if you’re 5 months pregnant has limited usefulness.
In fact, in this kind of situation, I'd assume women would still need to be monitored by a midwife for signs of pre-eclampsia, so there’s still stress involved.
A positive result is something the NICE guidelines committee commented could end in unnecessary intervention, even unnecessary early delivery, which would be dangerous and expensive.
And also not the smoothest way of starting motherhood.
The Good Stuff About The Tests:
Women who have had pre-eclampsia in the past, but are not suffering with it in their current pregnancy, may gain reassurance from a negative test. It could be a huge weight off their mind.
A positive result early in pregnancy could also mean women get channelled into the right specialist services, which is important for good outcomes.
Finally, the tests could help the NHS save money. More women being screened with these tests could mean less hospital admissions for women to be observed for signs of pre-eclampsia. The financial challenges the NHS is facing means this is an important factor to consider.
For more reading on screening tests in general, I can’t offer any better reading on this than Sara Wickham’s piece for The Practising Midwife here.
Though we may face being ‘too clever for our own good’ again and informed consent is as always the most important thing to aim for, I want to end this post with gratitude.
When I was a third-year student I did a placement in Ahmedabad, India and I vividly remember asking the nurses how women were screened for pre-eclampsia and they said:
They come in when they're frothing at the mouth and fitting.
I’m thankful to live in a country where there's research ongoing and an NHS full of professionals who are often able to make a great deal of difference to the wellbeing of women and babies.
On that note I’d be fascinated to hear from you on any of the following points, or anything else pre-eclampsia related:
1. Do you offer these tests in your unit yet? Have you heard about them? What's your opinion?
2. Anything here that you’d like to add?
3. Any insights into pre-eclampsia, either professionally or personally you’d like to share?
Much Love, Ellie x