How Do Pregnancy Tests work?
Pregnancy tests are designed to test either urine or blood for a hormone called human chorionic gonadotropin (hCG). Here’s how it works: During conception, the sperm fertilizes the egg in the fallopian tube and then makes its way toward the uterus. It takes an average of 9 days for the fertilized egg to implant in the woman’s uterine wall. About 6 days after implantation, a woman’s body will start producing hCG as the placenta develops. The further along you are after conception and implantation, the more hCG is found in your blood and urine.
Types of Pregnancy Tests
Urine tests simply test for the presence of hCG. If the hormone is present in your urine, the test will show a positive result. When used according to the directions, urine tests can be up to 99% accurate depending on the amount of time that has passed since implantation and the stage of your menstrual cycle.
Blood tests also test for the presence of hCG, but in-depth blood work analysis can measure the specific hormone levels to indicate the possibility of twins or pregnancy complications. Pregnancy can be detected earlier through a blood test, as soon as 6 days after ovulation, but results from a blood test take longer to process than urine tests.
If you carefully follow the home pregnancy test directions, the result can be very accurate. However, getting a false negative or false positive result is possible if the test is taken too soon after conception or directions aren’t followed closely. Medications, drugs and extremely high levels of protein can also skew results.
Contact the compassionate pregnancy care physicians at All About Women care about your health. We can answer questions and give you advice, whether you’re pregnant or not. Learn all about pre-pregnancy checkups and other women’s care topics by browsing our knowledge center and blog.