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Women's Services Encyclopedia

Pregnancy Test

This is a test for detecting a particular hormone known as Human Chorionic Gonadotrophin (HCG). In the first few days after conception, the egg implants itself in the wall of the uterus (womb). The developing placenta secretes HCG (hormone) in increasing quantities as the pregnancy progresses.

  • The HCG blood test may be reported as positive (pregnant), or as a quantitative value, which can be used to estimate the gestational age of the fetus.
  • HCG, which is excreted into the urine, is the basis for the home urine pregnancy test.

Unlike the urine test, the blood test can detect pregnancies as early as 7 days after fertilization (even before a missed menstrual period!). Mothers with twins will normally have correspondingly higher HCG levels.

This test is performed from a venipuncture specimen.

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