The Women's Health site reports that there are two different types of pregnancy tests. A blood test taken at a doctor's office detects the hormone, human chorionic gonadotropin (hCG), which indicates a woman is pregnant. A blood test can detect a pregnancy earlier than home pregnancy test kits (HPT). HPTs, used by most women before getting a blood test, detect the hormone in the urine. There are many reliable home pregnancy tests on the market, but a few are able detect HCG earlier in a pregnancy compared to others.
Study Results
In 2004, Yale-New Haven Hospital released a report indicating that home pregnancy test (HPT) companies that claim to be able to detect the hCG hormone the day after a woman misses her first menstrual cycle in fact mislead consumers. Of the 18 most-popular HPTs that year, only one tested by the "American Journal of Obstetrics and Gynecology" (ACOG) was able to detect a pregnancy that early: First Response.
Best Tests
When a woman becomes pregnant, her fertilized egg attaches to the lining of the uterus and her body begins producing the hCG hormone. During the first two weeks of pregnancy, hGC levels increase at a rapid rate. Home pregnancy tests are designed to detect hormone levels and reliably indicate whether or not a woman is pregnant. In the crowded market of HPTs, it's in a manufacturer's best interest to produce a product that detects the pregnancy hormone as early as possible. First Response proved to be that product detecting a lower level of HCG than its manufacturers even claimed, meaning that it detected pregnancies earlier than comparable HPTs.
The Other Tests
That is not to say that other HPTs are flawed. In fact, the only test that can be considered most reliable is the blood test taken in your doctor's office. Norman Ravski, MD, associate clinical professor in obstetrics and gynecology at the Yale School of Medicine explains that a beta hCG test measures the exact amount of hCG in the blood. It is possible for this test to be accurate in detecting hCG even before a woman's period is late, which First Response is capable of doing, but most other HPTs are not.
The Runner-Up
The second most reliable HPT kit on the market is Clearblue Easy, positively detecting pregnancy four days early 53 percent of the time.
They Are All Positive
The good news is that one week after a missed menstrual cycle, most HPTs will have reliable results. So if you missed your period and need to know right now if you are pregnant, either get your blood tested or use an early pregnancy testing kit.
