How exciting, you suspect you may be pregnant! But now you need to confirm if your suspicions are correct. How do you test accurately?
Types of pregnancy tests
- Blood test
- Urine test
What is the most reliable method of finding out if you are pregnant?
The most reliable method of finding out whether you are pregnant is to visit your doctor or lab for a blood test to detect the presence of the hormone human chorionic gonadtrophin (hCG), which is produced by the placenta shortly after implantation 6 to 12 days after fertilisation.
Types of blood tests
There are also two types of blood tests:
A quantitative blood (serum beta) test
This is the most sensitive, being able to detect hCG levels as low as 1mIU/mL.
Qualitative blood tests
This test generally has a threshold of 25mIU/mL and may be inconclusive or deliver a false negative if the pregnancy is very early.
Home pregnancy tests
You can also test for pregnancy at home using a home pregnancy test (HPT), which is able to detect the presence of hCG in your urine and will indicate a positive result when the hCG level in a sample reaches or exceeds the sensitivity level.
How accurate are home pregnancy tests?
Remember that the sensitivity of the pregnancy test determines how soon after conception pregnancy can be detected, so it is possible to get a false negative if you test too early. This means that you may be pregnant even though the test was negative.
About blood tests
A blood test is more accurate because it can detect the actual amount of hCG, and subsequent tests can measure whether the level is rising if the first test was inconclusive. This is also useful in dating the pregnancy accurately.
How soon can you take the blood test?
Although it is technically possible to test accurately as early as 8 days after conception, false negatives may occur up to 3 weeks after the act of intercourse that causes pregnancy. This is because conception may take place several days after the date of intercourse, so the date of intercourse is not necessarily the day of conception.
What are the other reasons for taking a pregnancy test
Pregnancy tests can also be used to determine the viability of a pregnancy by measuring the rate at which hCG levels increase. In a healthy pregnancy the level usually doubles every 2-3 days. If it does not increase as expected, this may indicate a risk of miscarriage or ectopic pregnancy.
An ultrasound at about 8 weeks gestation is usually recommended to determine the health and viability of the pregnancy.
Things to remember if you are using a home pregnancy test
If you are using a home pregnancy test, remember:
- It is important to follow the instructions to the letter.
- Different test kits have different sensitivity levels, so read the instructions to determine how soon you can begin testing – usually at least 2 weeks after intercourse, or after you have missed at least 1 period, or are experiencing pregnancy symptoms.
- The first morning urine is the best sample to use as it contains the highest level of hCG. Don’t drink anything first as this may dilute the hormone.
- A faint test band may indicate a positive result. It is best to re-test the following day.
- Evaporation lines may appear on a home pregnancy test after the reaction time, which is usually about 5 minutes, so make sure you read the test only within the reaction time specified on the instructions.
- False positive tests are rare, but they can occur. Make sure that you have taken the test properly.
- False negative results are more common than false positives. A negative result is not necessarily conclusive – you may be testing too early, or the results may be affected by medications you are taking, or you may not have followed the instructions carefully enough.
- The amount of hCG produced differs from woman to woman, which means that you won’t necessarily get a definite result on a home pregnancy test just because another woman at the same gestational stage did.
- Some fertility medications may affect the results of a home pregnancy test.