Along your journey to parenthood, one of the hardest times is what is affectionately known as the “two week wait”. Well, okay, maybe not so affectionately. These two weeks are the time after ovulation until the time when your period is actually due to start and when you can take a pregnancy test to see if you are actually pregnant this cycle.
Unfortunately, pregnancy tests do not run on magic – you cannot take one the morning after you had sex and assume that it will be positive, or negative.
How a Pregnancy Test Works:
In order for a home pregnancy test to show a positive result, something special needs to happen – an egg has to first be fertilized and then it has to implant itself in the uterus. Once this occurs, the pregnancy hormone hCG will begin to be secreted into the body.
A home pregnancy test analyzes your urine to see if there is any hCG (human chorionic gonadotropin) present.
Types of Pregnancy Tests
The two most common methods of testing for pregnancy are blood based pregnancy tests and urine based home pregnancy tests. Both test for hCG levels; the only difference lies in that the former tests its levels within the blood stream while the later in the urine.
A positive blood test will usually show a positive result 3 to 4 days after implantation, or roughly 9 to 10 days after ovulation.
For a home urine test, however, a positive result will not be visible until a week after implantation or until you have a missed period. Do not buy into the myth that certain urine tests can give a positive result before you have missed your period. In actuality, only 25 percent of pregnant women will receive a positive home pregnancy test 2 days before they have missed their period. Approximately 40 percent of pregnant women will receive a positive test result the day before they have a missed period. On average, it will take at least 13 days after ovulation for a urine test to first turn positive.
Factors To Consider
Several factors may affect the time it takes for a pregnancy test to first show a positive result. These include the date of ovulation, date of implantation, hCG levels in either the blood stream or urine, and the sensitivity of the test. The date of ovulation is of great significance in calculating when a pregnancy test might first show a positive result, because it signifies that ovulation occurred and fertilization took place. The amount of time either this process, or the process of implantation, may take will differ between women. Therefore, though one woman’s pregnancy test may show positive today, another’s may only become positive a day or two later even if they were to have conceived on the same day.
The hCG levels in the urine and in the blood vary greatly as to the definition of what is ‘normal’ or ‘high’ and this affects how early a pregnancy can be identified. Though you may be pregnant, if you have a low hCG level you will receive a negative result, and it would take a few days for it to become positive. However, if your levels of hCG are at a high level, the blood or urine test will instantaneously show a positive. Also varied is the concentration of urine levels throughout the course of the day. This is why it is recommended that a home urine pregnancy test be done with first morning urine, when urine concentration is at its highest.
Pregnancy tests also vary in sensitivity. Low sensitivity tests tend to detect pregnancy earlier than highly sensitive ones. Pregnancy test sensitivities are indicated in mIU/ml, therefore a test with a sensitivity of 40 mIU/ml will require twice the amount of HCG than that of a test which has a sensitivity of just 20 mIU/ml.