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Pregnancy Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Pregnancy Test

Pregnancy tests detect the hormone human chorionic gonadotropin (hCG) in urine or blood to confirm pregnancy.

Overview

The placenta produces hCG after a fertilized egg attaches to the uterine wall. Levels of this hormone typically double every three days during the first ten weeks of pregnancy. hCG is essential for thickening the uterine lining, preparing the body for labor, and stopping menstrual periods.

Types of Tests

  • Urine tests: Can be performed at home or in a clinic. They are 97–99% accurate when taken a week or two after a missed period.
  • Blood tests: Performed in a lab. They can detect smaller amounts of hCG earlier than urine tests but are less commonly used for routine pregnancy confirmation.

Clinical Uses of Quantitative Blood Tests

Quantitative blood tests measure the exact amount of hCG and are used to:

  • Determine fetal age in early pregnancy.
  • Monitor high-risk pregnancies for potential miscarriage.
  • Check for ectopic pregnancy or molar pregnancy.
  • Screen for birth defects or chromosome problems (e.g., Down syndrome).
  • Monitor certain cancers (e.g., ovarian or testicular).

Symptoms of Early Pregnancy

Common signs include:

  • Missed period
  • Swollen, tender breasts
  • Fatigue
  • Frequent urination
  • Nausea and vomiting (morning sickness)
  • Bloating

Important Considerations

  • False-negatives: Occur if a test is taken too early when hCG levels are not yet high enough to detect. If a test is negative but you suspect pregnancy, repeat the test in one week.
  • False-positives: Can occur if you are taking fertility medications.
  • Preparation: For urine tests, avoid drinking large amounts of fluid beforehand to prevent diluting the sample. Using the first morning urine is recommended for the highest accuracy.

Frequently Asked Questions

Quantitative (beta‑hCG) tests measure the exact hormone level. In a normal intrauterine pregnancy, hCG roughly doubles every 48‑72 hours. Slower rises or plateauing may indicate an ectopic pregnancy, miscarriage, or molar pregnancy, prompting further imaging (e.g., transvaginal ultrasound) and management.
Most over‑the‑counter tests are >97 % accurate when used at least one week after a missed period, because hCG has usually risen above the detection threshold by then. If you test earlier, consider waiting a few days and retesting for a more reliable result.
Yes. Excess fluid dilutes hCG concentration, making it harder for the test to detect. Using the first‑morning urine, which is most concentrated, maximizes accuracy, especially in early testing.
false‑negative often occurs if you test too soon (hCG not yet high enough), dilute your urine by drinking large amounts of fluid, or use an expired test. If you have pregnancy symptoms but a negative result, wait 48–72 hours and test again with first‑morning urine; if still negative and you suspect pregnancy, schedule a quantitative blood hCG test with your clinician.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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