Blood Tests for Pregnancy: Accuracy and Limitations

Quantitative hCG blood tests are highly accurate for pregnancy detection but not 100% certain. Limitations:

1. Early pregnancy – hCG may be below detection threshold (false negative).
2. Ectopic pregnancy – hCG rises but location unconfirmed.
3. Recent pregnancy loss – Residual hCG yields false positive.
4. Medical conditions – Certain tumors, hormonal imbalances, fertility drugs can elevate hCG.
5. Lab errors – Rare but possible.

Doctors combine test results with history, symptoms, and other diagnostics for definitive diagnosis.