I am interested in the size of the US market for the beta-hCG blood test.  

hCG (human chorionic gonadotropin) is a hormone produced in the
placenta during pregnancy.  The over-the-counter home pregnancy test
is a yes/no strip test that detects this hormone in your urine.  The
beta-hCG (or 'bhCG', 'quantitative hCG', or simply 'beta') is a blood
test usually performed by your doctor to confirm pregnancy.

Unlike the over-the-counter pregnancy test, the beta-hCG test provides
a quantitative result (the level of the hormone) instead of simply
detecting its presence.  Blood is usually tested instead of urine. 
The test is an ELISA type immunoassay.  The vast majority of these
tests are sent to the hospital laboratory or to lab services such as
Quest or LabCorp where they are performed on automated test equipment.
 A small number are done in-house in clinics that have their own labs.

Physicians order these tests to confirm pregnancies, to monitor
at-risk pregnancies, in the emergency room in the case of a woman with
abdomnial pain, in abortion clinics, and in fertility clinics.  Its
also a marker for some cancers (incl. testicular cancer) but I don't
expect that to be as significant a  number of tests.

I'd prefer an estimate of the number of these tests ordered in the US,
but the market size in dollars would also suffice (or simply the world
market if that is easier).

Some helpful numbers:
-There are approximately 4M live births annually in the US.
-600,000 miscarriages annually in the US
-1.5M abortions annually in the US

-The worldwide market for home pregnancy tests was $630M in 2004.
-For the beta, we have estimates for some Western European countries
of about tests/population of 1.75 or tests/pregnancy of about 1.25. 
Note that the testing rate is generally lower in Europe than in the
US.