Home Pregnancy Tests
Home pregnancy tests can find the presence of a pregnancy hormone (called human chorionic gonadotropin, or hCG) in a sample of urine. High levels of hCG are made during pregnancy. The home tests have similar results to the pregnancy tests done on urine in most doctors' offices if they are used exactly as instructed.
When a woman becomes pregnant, the egg is generally fertilized by a sperm cell in a fallopian tube (conception). Within 9 days after fertilization , the egg moves down the fallopian tube into the uterus and attaches (implants) to the wall of the uterus. When the fertilized egg implants, the placenta starts to develop and begins to release hCG into the woman's blood. Some of this hCG also passes in her urine. In the first few weeks of pregnancy, the amount of hCG in the urine gets higher very quickly-it doubles every 2 to 3 days.
There are two basic types of home pregnancy tests.
- The most common types of home pregnancy tests use a test strip or dipstick that you hold in the urine stream or dip into a sample of urine. An area on the end of the dipstick or test strip changes color if hCG is present, meaning you are pregnant.
- A second type uses a urine collection cup with a test device. To use this type of test, you may place several drops of urine into a well in the test device or you put the test device into urine collected in a cup. An area of the device changes color if hCG is present, meaning you are pregnant.
The first urine of the morning (that has collected in the bladder overnight) is the best one to use and has the most accurate test results.
The accuracy of home pregnancy tests is different for every woman because:
- The days of a woman's menstrual cycle and ovulation can change each month.
- The exact day of implantation of the fertilized egg is not always known.
- Each home pregnancy test kit has a different sensitivity to find hCG. If the level is very low, the first urine of the morning is the most likely to show a positive result.
While a few home pregnancy tests may be sensitive enough to show a pregnancy on the first day of a woman's missed period, most test kits are more accurate about a week after a missed period.