When you are trying to get pregnant, waiting to find out can be excruciating. Wouldn’t it be great if there were something that could tell you “Yes, you are pregnant” the moment you conceive? Well, unfortunately these things do not exist, so we rely on the home pregnancy test. These days, home pregnancy tests are extremely accurate, as long as you understand how they work and when to take them.
How Does a Home Pregnancy Test Work?
Home pregnancy tests are designed to detect Human Chorionic Gonadotropin (hCG), also known as the pregnancy hormone. The hormone is excreted as soon as the fertilized egg implants into your uterus, and your levels of this hormone double approximately every 48 hours from then on. Yet, they really are not high enough to detect in your urine until at least two weeks after conception.
Just to give you an idea of what the levels are like each week and how they increase, here is a guideline of hCG levels in weeks from your last menstrual period (LMP) :
- 3 weeks LMP: 5 – 50 mIU/ml
- 4 weeks LMP: 5 – 426 mIU/ml
- 5 weeks LMP: 18 – 7,340 mIU/ml
- 6 weeks LMP: 1,080 – 56,500 mIU/ml
- 7 – 8 weeks LMP: 7, 650 – 229,000 mIU/ml
- Non-pregnant females: <5.0 mIU/ml
- Postmenopausal females: <9.5 mIU/ml
Remember that this is just a general guideline. As every women’s pregnancy is different, their levels of hCG can rise differently as well.
When to Take a Pregnancy Test
In order to get the most accurate result from an at home pregnancy test, read the instructions and follow them precisely. Many times they will tell you to take it first thing in the morning, as this is when your urine is most concentrated. As far as when into your cycle should you take a test, your hCG levels should be high enough to get an accurate result when you expect your period to start.
False Negative Pregnancy Test
Now that you have a better understanding how pregnancy tests work, I think you can figure out why false negatives are so common. In fact, it isn’t really even a false negative; it just means that your levels of hCG were too low at the time for the test to detect. So, if you think that you are pregnant and get a negative result, just try again a few days later.
As each brand of pregnancy test is different, and they each have a different calibration for detecting hCG levels – some are more sensitive than others. The more sensitive ones would be able to give you a positive test earlier, and some brands even claim to detect pregnancy before your missed period.
Positive Pregnancy Test
It is extremely rare to get a false positive result on a pregnancy test, but it can happen. But usually, no matter how faint the line, plus sign, words, etc. may be, if you can see it at all, then it is likely a positive pregnancy test result. This would be the time to call your obstetrician or midwife and set up your initial prenatal appointment.