Whether women are desperately hoping they are pregnant, or desperately hoping
they are not, they want to know as quickly as possible. There are basically
two types of pregnancy tests: blood and urine. Both measure the levels of hCG
(a hormone released by a fertilized egg). The levels of hCG rise rapidly after
a woman becomes pregnant, but there needs to be a certain amount in the body
before a test can pick it up.
Blood tests are the most accurate and sensitive, while urine tests take a little
longer. Although the instructions on most home pregnancy tests will say that you
need to wait until two weeks after a missed period, the reliability of any
pregnancy test has nothing to do with whether or not you have missed your
period. The only factor is how long a woman has been pregnant.
Most at-home pregnancy tests achieve 95 percent accuracy three to four weeks
into a pregnancy, so they use "two weeks after you have missed your period"
as a type of shorthand. The urine tests used by a doctor are more sensitive and
can pick up a pregnancy one to two weeks following conception. Blood tests
(which are performed by a medical doctor) are the most sensitive of all, and
can often detect a pregnancy six days after fertilization. However, some new
forms of at-home pregnancy tests are starting to hit the market that are almost
as effective as the kind previously available only to doctors. They are said to
be effective within a day following a missed period.
You will notice that all of these date ranges have to do with the time since
fertilization. It is entirely possible to have intercourse but not actually
become pregnant for several days. So, my best advice is to wait and see if you
miss your period. If you do, then you take a pregnancy test (knowing that the
longer you wait, the more likely the results will be accurate). If the test is
negative, but you still don't get your period, you should follow-up with
another test two weeks later. Good luck.
