NHS not using accurate info in the 12 week screening calculation- why?

[YellowLeavess]

I had my 12 week screening test done yesterday and I wondered if what I experienced was standard practice.

First of all - my weight. I was weighed, and the scale showed 3.5lbs more than I actually am. (I weigh myself daily and track it.) The nurses said they do not account for the weight of the clothes etc, and simply wrote that figure down instead. So the data point (my ‘weight’) being used to calculate the trisomy risk is not correct, which will lead to an inaccuracy in the final risk score.

Also, if it’s an IVF pregnancy then they use the age of the woman at the time the egg was collected. This obviously makes sense and is the correct thing to do, as any chromosomal issues are formed at the point of conception.

So for natural pregnancies, why don’t they use the age of the woman at the time she conceived - i.e. the age of the egg, as with IVF pregnancies? Instead, they recorded my age as the age I’ll be at birth. But again, that’s inaccurate and will lead to an error in the final risk score.

Both of these inaccuracies are going to artificially increase my risk profile which is going to cause a greater level of anxiety and stress. Why don’t the NHS want to use the best, most accurate data to input into the risk equation?

I say this with kindness, but you are massively overthinking this. First of all, I've had shits bigger than 3.5lbs. It's an insignificant difference. Ditto a single year being added to the mothers age between conception and birth. Is there a reason you are overly worried about your risk? Have you raised your increased anxiety with your midwife as you may need/want extra support during the pregnancy

Kindly, I'm not sure that that minimal weight or age difference will have a big difference on the risk profile. And it will be the same for everyone. I'd really consider if weighing and recording your daily is a very healthy habit, are you getting support for your anxiety?

If you are that worried about the results have NIPT instead. That’s what we did.

None of the things you mention are at all significant- combined screening is hugely inaccurate anyway.

Agree with other posters, you need to relax. Neither of those things are going to make any material difference to your risk. If you are feeling this anxious in general you really should speak to your midwife x

I was fatter and older with my second pregnancy and got a 'better' result on that screening than with my first. I don't think a year and a few pounds will make any difference.

At a guess, not only will these have a minimal impact on the calculations, but the calculations themselves will have been formed using data collected in this way, so the inaccuracies cancel each other out, as it were.

I’m a scientist by trade. My issue is that crap data in, equals crap data out. I’m just surprised that the NHS doesn’t want the ‘data in’ to be as accurate as possible. They are generating risk equations which can really impact on women’s state of mind. I was unimpressed by the lackadaisical approach to not getting the best and most accurate risk score, and wondered if this was something happening nationally or whether it’s just my hospital.

And yes, a year either way can really affect the screening score - especially when the woman is getting older - try it out on some of the online calculators.

Similarly, 3.5lbs is enough to take someone from a healthy BMI to an overweight BMI - or even overweight to obese. Of course that is going to have a huge effect on the resultant ‘risk score.’

PS - if you are having bowel movements that truly weigh 3.5lb then I advise you to speak to your GP!

I'm a scientist too, but I was fine with the calculations. It might take you from a tiny bit under a threshold to a tiny bit over one, but if you're that close to the edge, perhaps you'd want all the information you can get about a potential issue?

Nope, I stand by my first response, you are massively overthinking this and I would seek help for your anxiety. You may be a scientist, but that doesn't mean you don't have abnormal levels of worry about this. It isn't healthy to be so obsessive

How do you know its not your scales a couple of pounds out?

as far as I’m aware maternal weight is not a significant risk factor for trisomies and anyway the NHS will always use their own reading/scales rather than the ‘correct’ weight you’ve reported for very obvious reasons (clearly, it is more accurate whatever you say!)

also I think every older mother will know that the risk increases with age so would not be expecting a very low risk score. 1 year (or 9 months) is going to make very little difference and anyway the probability generated is completely meaningless for most people, unless further testing is then recommended. The age/weight parts are least scientific and will be having the lowest impact on the risk score (clearly noting that a 45 yo woman is going to get a very different probablility to a 25 yo but 35 vs 36 will make no noticeable difference.

I’ll say it for the third time (in case you didn’t believe me the first two times), I find it difficult to understand why they would use suboptimal data points in calculating such important scores. That is why I started the thread. I’m curious by nature. You seem to have mistaken this for a host of diagnoses:

I would seek help for your anxiety.

You have abnormal levels of worry about this

It isn't healthy to be so obsessive

Thankfully, my mental health is robust. (And, I received a low risk NIPT and the 12 week scan was all good.)

Nonetheless, I would urge you to think twice about posting such statements on the Pregnancy board in future though, as other posters may not be doing so well, and would be quite hurt by your insensitive comments.

If you're a scientist, surely you appreciate that they need to use verifiable information?

You're saying that you're 3.5lbs heavier than normal today - but you could actually be 5lbs lighter. The NHS has no way of knowing. Or you could have not eaten for two days before. They've just got to use the weight on the scales.

Many women don't know exactly when they conceived, even if they track. Sometimes it's late. They use your current age, but then the dating of the pregnancy, which is done on measurements taken at the 12 week scan...

But really, while good data = better outcomes, small changes really don't change your risk margins much, and if you come back with higher risks, you get further tests. It's a screening to see if you need that further diagnostic.

@YellowLeavess Thanks for the advice on where and what to post but I have a sneaky suspicion that I've been doing this longer than you have. PFB at all?

If you had NIPT why did you have the combined screening? Our trust doesn’t do the combined test if you have already had NIPT as it tells them absolutely nothing extra and is a waste of resources.

What kind of Scientist? I could assume that a Physicist or Chemist might struggle with the variability in Biological or Environmental science. The calculations are not that precise.
There is no use in being more precise than the accuracy given the standard deviations.

While you have a point about the data, I'm a data analyst myself so I do get the need for accuracy, literally nothing they put in the calculator will actually effect the outcome. They could put you at fifty stone and 100 years old and it would give you some kind of mega risk score, but that wouldn't actually make any difference to the health of your individual baby.

These risk scores are often inaccurate, as are the scans - we all know people who have been told their baby is going to be massive from a scan and it turns out a perfectly normal weight etc. So my advice to you would be to think about how accurate you need your risk assessment to be personally. If you need to know for sure, there are more diagnostic tests that can be done privately for example. Because either way, a risk score is just a risk score. Even if yours is a one in a million chance of there being a problem, you could still be that one.

I wouldn't get too hung up on the process here, the risk score isnt diagnostic anyway and is just an indication - even if the data collection was perfect it still can't tell you if your own baby is 'ok' or not.

But they can't take at your word that your weight is that different to what they see on the scales in front of them. They have to use their verifiable source as the data point, not anecdotal reports from the mother.

And when it comes to ages, if their policy is to note the mother's age at birth rather than current age, perhaps the risks are calculated based on the age of the mother at birth rather than at conception / during pregnancy.

Weight goes up and down 3.5lb based on time of day you weigh and scale you use, why are your scales right and theirs wrong?

I totally disagree. I would want to help someone who seems to be having very irrational worries, especially if your screening was fine. I'm concerned your weight obsession will have a negative affect on your future child as they grow up.

Self reporting of weight is notoriously inaccurate. As others have pointed out what you have eaten, whether you have had a bowel movement, a full or empty bladder, times of day etc etc could affect your weight. Your scales won’t be perfect - their scales probably aren’t either! They cannot make it perfect but the data will be good enough for a meaningful result.

I get your point but honestly there are so many things like this you're going to question throughout your pregnancy and postpartum care that I'd advise you to drop it and move on mentally. The NHS is a slow to progress machine that works with it's own rules!

Have to say I'm intrigued to know what kind of scientist you are that measures weight in imperial? I do not believe for one second that the scales used in the clinic were anything but kilos, as would the calculations have been you refer to.
Babies are weighed in kilos too by healthcare despite parents continuing to use pounds. Start getting your head round it now, it'll make it easier to communicate with your midwife/HV etc.

I presume they’re basing risk factors on the large swathes of data that they collect from pregnant women, and this will have largely been collected in the same way, so the same variances can apply for everyone? At my 12 week appointment I was weighed with my coat, shoes and handbag on!

My issue is that crap data in, equals crap data out.
but what’s the option here? Take the woman’s word on her weight? - that’s crap and likely incorrect data
or ask her to strip, which some (most?) women will find stressful, just for the sake of clothing weight, which will cause minimal difference. And then what? What about the women you weigh at the end of the day, who need to pee and poop and have eaten 3 meals, between the women you weigh in the morning or those who haven’t eaten or drank anything? It’s virtually impossible to get this exactly right and the same for every patient. So they do it the way they do. The worst case is you get a higher risk, and then they send you for more testing, which though stressful, won’t impact most women and the women it does impact get expensive additional screening that is useful to them.

And the age thing, what if the woman doesn’t know when she conceived? What if she had a birthday that month (which is presumably very common!) and then the dates are slightly unclear or innaccurate. Surely it’s better to go with the more high risk number (age at birth), and get a ‘worst case’ risk calculation than to give her an inaccurate lower risk score?

i do think you’re being a bit intense about this, and I know you don’t appreciate pps comments but it reads like you’re worried about being noted at 3lbs heavier and a year older. Which really isn’t important. I know you’re saying it’s not that but if you are a scientist you know no method is perfect, it’s about finding one that is the best overall option.

What kind of scientist is still using imperial measurements?

My parents are in their 70s and use metric for weight. I'm in my 40s and have always used metric for weight. NHS definitely did for my weight at 12 week scan.