Evolution of Pregnancy Testing Methods

Aug 3, 2024

Lecture: History and Science of Pregnancy Tests

Ancient Pregnancy Tests

  • Date: 1350 BC
  • Location: Ancient Egypt
  • Method: Urinate on wheat and barley seeds
    • If either sprouts, the woman is pregnant.
    • If wheat sprouts faster, it's a girl.
    • If barley sprouts faster, it's a boy.
  • Modern Study (1963):
    • Found 70% accuracy in predicting pregnancy
    • Could not reliably determine the sex of the baby
  • Hypothesis: Pregnant women's urine contains more estrogen, promoting seed growth.

Modern Pregnancy Tests

  • Hormone Detected: HCG (Human Chorionic Gonadotropin)
    • Produced in the early stages of pregnancy
    • Prevents the shedding of the uterus lining
    • Supports placenta formation

How Over-the-Counter Tests Work

  1. Application: Urine is applied to the strip.
  2. Fluid Movement: Urine travels up absorbent fibers through three zones:
  • Reaction Zone:
    • Antibodies (AB1) attach to any HCG in the urine.
    • Enzyme linked to AB1 activates dye molecules.
  • Test Zone:
    • More antibodies (AB2) bind to HCG.
    • HCG is sandwiched between AB1 and AB2, activating dye to show results.
  • Control Zone:
    • Confirms the test's functionality.
    • Unbound AB1 enzymes activate dye if present.

Reliability and Issues

  • False Negatives:
    • Low HCG levels (too early in pregnancy)
    • Diluted urine samples (recommendation to test in the morning)
  • False Positives:
    • Sources of HCG other than pregnancy (IVF injections, ectopic pregnancies, certain cancers)
    • Possible for men to get a false positive
  • Doctor's Confirmation:
    • More sensitive and quantitative tests
    • Exact HCG levels determined from blood tests

Scientific Method in Pregnancy Tests

  • Pregnancy tests demonstrate the scientific method:
    • Ask a question
    • Perform a controlled experiment
    • Analyze results to check hypothesis
  • Modern tests provide quick results without waiting long periods.