This article is from the Pregnancy Screening FAQ, by Lynn Gazis-Sax (gazissax@netcom.com) with numerous contributions by others.
From Robbrenner@aol.com (Robert Brenner MD)
2. HCG is human chorionic gonadotropin. It is secreted by the
placenta and is measured by pregnancy tests. Urine pregnancy tests
can turn positive as early as 2 days after a missed period. I
recommend doing a urine pregnancy test when 1 week late for the period
to lesson the incidence of false negative results. Serum pregnancy
tests can turn positive around the time of the missed period but again
I wait til the patient is 1 week late to avoid false negative
results. Essentially all over the counter pregnancey tests are the
same. In a normal pregnancy HCG levels should double every 3 days.
This is measured by quantitative serum HCG tests.
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