Most of us believe that home pregnancy tests are more than 99% accurate - that you can trust the results after peeing on a stick. But early pregnancy tests (ones that are marketed to use before your period is due) are not 99% accurate, ironically if you use them as early as marketed.


6.5% ‘wrong’ results

We first heard about the issue in our forum; each week we saw stories of confusion, panic and heartbreak. So we decided to do our own investigation, with a survey of 1166 MadeForMums users who’d used 1541 early pregnancy tests. Our survey showed that early pregnancy tests are leading to 1 in 15 (6.5%) tests giving false or misleading results.

We found:

  • 5.5% of the pregnancy test results you got were ‘false’ negatives. This means getting a negative result when in fact you later find out you are pregnant
  • 1% were ‘false’ positives. This means getting a positive pregnancy result, when you later find out you’re not pregnant

The consequences of both can be enormous.

Getting a false positive pregnancy test

False positives are rare – but our research shows they happen more frequently than many health professionals realise. When using an early pregnancy test, the most likely (and heartbreaking) reason for getting a 'false' positive is that you've naturally lost your pregnancy in the very early stages.

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This means they're not really 'false' in an incorrect way, but they do give women the false hope that they have an established pregnancy.

“We don’t know how common these ‘pre missed-period miscarriages’ are,” explains Neil McClure, Professor of Obstetrics and Gynaecology at Queen’s University Belfast, “but we believe it happens as part of the body naturally selecting only the healthiest embryos. It doesn’t mean there is anything wrong fertility-wise or that anything needs investigating medically."

“Early pregnancy tests pick up these ‘pre missed-period miscarriages’ causing a lot of distress for women who understandably feel that they have ‘lost’ a baby,” explains Professor McClure. “This could be avoided if women waited to test until the first day of the missed period.”

And that's one of the key issues. An early pregnancy test may detect that your egg has been fertilised but sadly this doesn't mean it will lead to an established pregnancy. This is called a ‘chemical pregnancy’ – an early miscarriage, which is only detected by a (chemical) pregnancy test.

So this is the question you have to ask yourself. How would you feel if you found out you'd been in the very early stages of pregnancy but then lost the pregnancy? Many women understandably grieve for their miscarried baby, and some have told us it's made them much more anxious in the early weeks of a subsequent pregnancy. Would you rather know - or not know? Taking a pregnancy test early might reveal this to you.

On our forum, milliepop explained how she got her bfp (big fat positive) result one Sunday but then started bleeding on the Friday and a second test proved negative. "It really doesn't matter how early it was, it still hurts. I was OK when it actually happened and found comfort it was so early, but it hit me when I got my letter through for my booking-in appointment. I then realised what I'd lost and what could have been."

Getting a false negative pregnancy test

As well as being distressing, a false negative can lead to unintentional harm to your unborn baby through lifestyle choices you make because you think you’re not pregnant.

One mum told us, “I took a test and truly trusted the negative result. It was Christmas and so I had a few drinks. I would never have had a drop of alcohol if I’d known I was pregnant. The pregnancy ended in miscarriage and for a long time I had a huge amount of guilt and blamed myself, wondering if the drinks had anything to do with it.”

Why early pregnancy tests are confusing

Since they first went on sale over 10 years ago, early pregnancy tests have becoming a substantial part of a booming industry that sells around 12.5 million home pregnancy tests in the UK each year.

But we think there's way too much confusion around using these early tests.

Firstly, there's the packaging. They’re marketed with two bold claims on the packaging: firstly that you can use them from 3 to 6 days before the first day of your missed period, and secondly that they are more than 99% accurate.

However, what’s not clear is that these two statements are mutually exclusive. In fact, most early tests only claim to be more than 99% accurate when you use them from the day your period is due. In other words, that's when normal pregnancy tests are taken.

If you take an early test before this date then the accuracy rates drops significantly. For example, a First Response Early Result will only detect a pregnancy in 62% of women when used 6 days early as advertised – that’s a 1 in 3 chance of being wrong. Yet this vital information is only written in small print - on the outside of the box and then again in small print within the instructions that are 1000 words long.

Not only is the small print too small – it’s also confusing. Different brands describe the day from which you count in different ways:

  • Clearblue - talks about "the day your period is due" - this clearly means the day your period is due
  • First Response - talks about "the day of your missed period" - this means the day after your period is due
  • Predictor - talks about "the day you miss your period" - this means the day after your period is due

The results of our research make a strong case that better industry standards are required. At the very least, let’s have an agreed consistent day from which to measure.

In addition, there's competition between the early test brands for just how early you can start testing. First Response claims "Six days before the day of your missed period" while Clearblue says "Four days before your period is due". Given they're measuring from two different days, you can use First Response five days before your period is due and Clearblue four days before - so there's only a day between them. Confused? We certainly are!

“Manufacturers of pregnancy tests need to write information in a way that’s very clear and is easy to read,” says GP Dr Rob Hicks. “Just like with medicines, doctors will always advise that patients read the instructions and information but how many people actually do?”

So how important is an accurate result?

Very important – so you tell us. Our survey showed that 95% believe a 99% accurate result is more important than taking a pregnancy test as early as possible.

Yet, we found that only 47% of you took your pregnancy test during the 99% accuracy window - suggesting that most of these tests are used early. This is understandable as we know how important it is to know as soon as possible whether you’re pregnant or not. That two week wait can feel like an eternity.

In other words, we crave accuracy first and foremost, but the conflicting information on these tests is making it difficult for us to be sure when the test is accurate and how much we can trust the results we get.

“We know we should wait till our period’s due but it’s so hard to resist testing early. Nobody knows about all this - unless you’re trying for a baby, it’s a secret world of raised hopes and disappointment,” one woman told MFM who then revealed that she’s stopped using the early tests because of the distress that they can cause.

What Clearblue says

We asked the two leading early pregnancy test manufacturers, Clearblue and First Response, for a reaction to our findings. Clearblue replied almost instantly, saying, "Our own extensive research in the field agrees with your finding that accuracy is the number one most important attribute every women demands in a pregnancy test.

"We run a large study every few years with women across 5 countries, at very different stages of the life, and that view is consistent. However, what this research also tells us is that up to 40% of women want to test before their expected period. Their result is so potentially life-changing that they don’t want to have to wait."

Why this issue matters

Home testing kits are now the standard way of testing to see if you’re pregnant, often used long before a visit to the GP.

And as most mums will testify, knowing whether or not you’re going to have a baby is the moment at which your life changes forever. These tests are often taken in a state of anxious expectation, and so confusing instructions and tiny small print is not what we need.

It’s especially true for the many women who are desperate to become pregnant having experienced multiple failed attempts in the past. On the other side of the equation, accurate test results are equally vital to women who really don't want to be pregnant at this point in their life.

Why early tests are less reliable

Pregnancy kits test for the hCG (human chorionic gonadotrophin) hormone - sometimes called the pregnancy hormone. If you are pregnant, the day after your period is due the levels of hCG are likely to be around 100 milli-international units per millimetre (100mIU/ml). Early tests measure at a lower hormone level (as low as 25mIU/ml for Clearblue while the Predictor test claims to detect hCG at 12.5mIU/ml), which allows for a much earlier response. For most women, the strength of this hormone doubles every two to three days in early pregnancy.

“When pregnancy tests are taken on the first day of your missed period, as long as you have a regular monthly cycle, they pick up pretty much 99 percent of pregnancies accurately,” explains Professor McClure.

“If however, you test earlier than this, when levels of hCG are much lower, your results may be less accurate.”

Dr Luke Koupparis, GP from Westbury-on-Trym near Bristol, also has concerns about the reliability of early tests. “The message is that you can’t rely on these tests until the pregnancy is fully established with adequate hCG levels and that this is not the same in all women. However, it is more likely in the days after your period is due.”

As well as testing too early, another likely culprit for false negative results is that so many women have irregular cycles. “If a negative test later becomes positive you’ve probably just ovulated several days later than you thought and tested too early,” says Prof McClure.

“My advice to women would be to try and resist the impatience to find out early and wait until the first day of their missed period. This way you’ll avoid unnecessary grief at what is already an emotional time.”

Should you wait to wee?

While medical experts like Professor McClure will naturally encourage women to wait, we understand that early pregnancy tests have their place. There will always be women who want to know as soon as possible.

Our argument is that you need to know all the facts before you decide to take an early test.

If you do take a test earlier than the day after your period is due, you can’t be sure the result is correct. If you’re happy knowing this, and can wait for a few days before taking another test to be sure, then an early test should work for you. However, if you know you’d be devastated if a test shows positive and then you find out you’re not pregnant a few days later – it’s so much better to wait.

And if you’re someone who will take a test every day, just to see if the negative will turn positive – is it really worth the emotional strain?

The results of our survey make it clear that these early tests need to have clearer labelling on the packaging and standard instructions inside – so you have all the information before using them.

In short, for millions of women, eager to use these early tests correctly, we need more clarity and less false hope.

That’s why we’re launching our #WaitToWee campaign – if you want to be sure if you’re pregnant or not, wait until the day AFTER your period is due.

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