When can I take a pregnancy test?

Trying for a baby can make for an incredibly frustrating time and waiting to take that test each month can be torturous!

When can you test?
The technology behind home pregnancy tests has advanced greatly in the past few years and we can now take tests much sooner and still expect a reliable result. However, there is a risk that testing too early could mean getting it wrong. So, when is the best time to take a pregnancy test?

Officially, the most reliable time to take a pregnancy test is after you have missed a period.

It's likely that the length of your cycle varies on a monthly basis, so the best way to work out when to expect 'Aunt Flo' is by monitoring the length, pattern and variability of your menstrual cycle.

Taking a pregnancy test after your longest expected cycle is most likely to provide you with a correct result. However, waiting this long can be absolutely agonising so many choose to test earlier.

Of course, it makes sense that you find out whether you are expecting as soon as possible but being too eager could affect the result. So, one of the best ways to make sure you get an accurate result from an 'early' pregnancy test is by understanding how they work and making sure you use them effectively.

How do pregnancy tests work?
Pregnancy tests detect the presence of the hormone hCG (human Chorionic Gonadotropin) in urine. Once a pregnancy is conceived and implantation in the womb lining has taken place, hCG is passed from the developing foetus to the mother-to-be's blood via the placental tissue. Because of this, pregnancy tests can only give a positive result after implantation (and not just fertilisation) has occurred.

The length of time between fertilisation and implantation varies between pregnancies and individuals but is on average 6 - 12 days after ovulation. This means that the earliest day you can test and expect to get a positive result is seven days after you have ovulated.

That said, you should bear in mind that if you test this early there is a chance that implantation will not yet have occurred and you may get a false negative. For this reason it is usually best to take another test 3 or 4 days later.

Sensitivity
The amount of hCG increases rapidly throughout the first stage of pregnancy and levels double almost daily which is why test results are more reliable the further along a pregnancy is.

As older tests could only detect the higher levels of hCG present several weeks after implantation, women had little choice but to wait. However, the new range of pregnancy tests available are sensitive enough to detect significantly lower levels of hCG in the blood and so are able to provide a positive test earlier on.

Home pregnancy tests all have different sensitivities which means that they differ in the amount of hCG that needs to be present in urine before they are able to give a positive result.

If you are looking to test earlier on you should look for a pregnancy test with a high level of sensitivity. This will be expressed as a number on the box and typically ranges from 20ml/U (very sensitive) to 150ml/U (less sensitive) with lower numbers indicating increased sensitivity. If you test early on with a low sensitivity test you are unlikely to get a positive result even if you are pregnant (false negative).

How reliable will the results be?
The reliability of most pregnancy tests varies between 97 and 99% accuracy when they are used in 'optimum circumstances'. To make sure the result of your test is as accurate as possible you can try the following...

• Carefully read and follow the instructions on the testing kit box
  
  
• Test when you go to the toilet first thing in the morning as if you are pregnant levels of hCG will have accumulated overnight and will be easier to detect.
  
  
• If you test in the day try not to drink lots and lots of water before hand (although obviously don't dehydrate yourself) as this will weaken the presence of any hCG in your urine.
  
  
• Check the test result after the recommended length of time as if you leave it too much longer the result may be compromised.
  
  
• Regardless of whether you tested early or not it is advisable to repeat the test 3 or 4 days later to confirm the result.

So, when can I test?
If you are monitoring your cycle using bbt or other charting methods, the earliest you can test is 7 days after ovulation (using a sensitive test), although the longer you leave it before testing the more reliable your result is likely to be.

Visit the AskBaby forums to share your tips and tricks, frustrations and concerns with other AskBaby members who are trying to conceive.