A pregnancy test is designed to tell you if you are pregnant or not; however, how they work is important to understand so that you know which test to use and when it’s too early to tell.
Home pregnancy tests are extremely accurate, so if it says you are pregnant, you are almost certainly pregnant. If it says you are not pregnant, it might be too early to tell, or you are not pregnant.
The urine or blood test detects a specific hormone, human chorionic gonadotropin (hCG). This hormone starts being produced immediately after a fertilised egg attaches to the wall of the uterus, which usually happens about six days after fertilisation of the egg.
When you’re pregnant, hCG levels double every couple of days.
At-home urine pregnancy tests
You can buy these tests in supermarkets and pharmacies, or online. These tests are much more accurate than they ever used to be, and you can take a test before your next period is even due.
Most women don’t realise they are pregnant – unless they are trying – before a period is missed. Home pregnancy tests are accurate, inexpensive, and convenient.
Home pregnancy tests are usually a stick, where you pee on the correct end (follow the instructions!) and then a line or two lines will appear, with two lines usually meaning pregnant and one line meaning not pregnant.
Once you have a positive test, you can see your doctor, who will confirm the test with a blood test.
The best time to do a home pregnancy test
First thing in the morning, when your urine is the strongest.
False-positive test results at home
Rarely, you can get a false-positive, which means the test says you are pregnant, but you are not. This might occur if you do the test very close to your period or if blood or protein is in your urine.
Some drugs can also cause false-positive results, such as tranquilisers, anticonvulsants, and hypnotics.
Reasons a test might say you are not pregnant when you are
- The test was past its expiry date
- The test wasn’t done right (you peed on the wrong area)
- You tested too early, and hCG levels are not high enough to detect yet
- You drank too much water before the test, and your urine was diluted
- You are on some medications (diuretics, antihistamines)
If you are sure you are pregnant, but the test is negative, or you want to be sure, wait a couple of days and try again first thing in the morning.
Blood tests at the doctor’s office
Blood tests are more accurate than home pregnancy tests because they can detect pregnancy very early on – at 6-8 days after ovulation. Tests take longer to get results back from, and you must be at the doctor’s to do the test.
There are two types of blood tests:
- Qualitative hCG test – checks if hCG is present, yes or no.
- Quantitative hCG test (beta hCG) – measures the exact amount of hCG in your blood, helpful in tracking problems with a pregnancy, can rule out ectopic pregnancies or monitor a woman after a miscarriage.
References1
- 1.Butler SA, Khanlian SA, Cole LA. Detection of Early Pregnancy Forms of Human Chorionic Gonadotropin by Home Pregnancy Test Devices. Clinical Chemistry. Published online December 1, 2001:2131-2136. doi:10.1093/clinchem/47.12.2131
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