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Pregnancy Test Info

Further Information on Pregnancy Tests

How do pregnancy tests work?

All pregnancy tests detect the presence of hCG (human chorionic gonadotropin) in the urine or blood of a pregnant woman. HCG is released by the placenta shortly after a fertilised egg has implanted in the walls of the uterus. 

If you are pregnant, the level of hCG increases daily. The amount of hCG in your urine should approximately be:

DPO - Days Past Ovulation

Urine of Pregnant Woman

10

25 mIU/ml

12

50 mIU/ml

14

100 mIU/ml



Note: mIU – stands for million International Units 

Non-pregnant females:

What makes early pregnancy tests different from regular pregnancy tests?

Early pregnancy tests are designed to detect the smallest amount of hCG possible in the urine of a pregnant woman. Often, it is assumed you need to wait until you miss your period before you can take a pregnancy test. With sensitive early pregnancy tests, this is not the case. You may test as early as ten days past ovulation.

Sensitivity of early pregnancy tests

Please see the table below. The LOWER the sensitivity of a particular pregnancy test, the earlier that pregnancy test can detect a pregnancy:

First Response 

6.3 mlU sensitivity

Generic Ultra Early Pregnancy Test Strip 

10 mIU sensitivity

Generic Early Midstream Pregnancy Test

25 mlU sensitivity

Generic Cassette Format Early Pregnancy Test

25 mlU sensitivity

Generic Early Pregnancy Test Strip 

25 mlU sensitivity

Clearblue Midstream/Clearblue Digital 

50 mlU sensitivity


How early can I test for pregnancy?

Combining the two tables above gives the following guidelines of how early you can use each test to detect a pregnancy: 

DPO 
Days Past Ovulation

Urine of Pregnant Woman

Appropriate Test

< 10

5 – 25 mIU/ml 

First Response 
Generic Ultra Early Pregnancy Test Strip

10

25 mIU/ml 

Generic Early Midstream Pregnancy Test
Generic Cassette Format Early Pregnancy Test
Generic Early Pregnancy Test Strip

12

50 mIU/ml

Clearblue Midstream/Clearblue Digital

14

100 mIU/ml 

All of the above

 

How accurate are the results of early pregnancy tests?

The accuracy of the results of early pregnancy tests can vary from woman to woman. This may be due to a number of factors:

  • Uncertainty or miscalculation of the date of ovulation.
  • Due to the above, uncertainty of the date conception took place.
  • Based on the above, uncertainty of the date implantation into the lining of the wall of the uterus took place.

All of the above can lead to less than expected levels of hCG in the urine of a pregnant woman. Thus if a test with a sensitivity of 25 mIU/ml is used, and the actual number of days since ovulation is less than 10, the test will probably not return a positive result, even though the person is pregnant. The level of hCG has just not built up to a sufficient level to register a positive result. 

It is always advisable to repeat a pregnancy test after 24 - 48 hours. 

Recommendations for early pregnancy tests
Regardless of the pregnancy test used, or the calculated number of days since ovulation or since conception, we recommend the following guidelines:

  • Always test using first morning urine, when the level of hCG is at its highest / most concentrated.
  • Do not drink lots of fluids before taking an early pregnancy test as this may dilute the level of hCG.
  • Repeat the pregnancy test 24 - 48 hours after the initial test was taken.
  • Follow the pregnancy test instructions exactly. Read through the instructions from the beginning right to the end before starting the testing procedure.

Disadvantages of early pregnancy tests
Sadly, a very high number of pregnancies end with a miscarriage - it is estimated that this may be as high as 25% of all pregnancies. 
Taking a pregnancy test before your period is due, and getting a positive result may end with heartbreak if the baby is lost very early and the period arrives at its normal expected time.