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The Science Behind the Accuracy of Pregnancy Tests and Knowing Sooner

The cell that originates when a fertilized egg is implanted in the uterine wall initially secretes a pregnancy hormone variant hCG-H. As such, this hormone is actually produced in the earliest stages of pregnancy before the primary pregnancy hormone, hCG, which is produced immediately following implantation by a different set of cells.

The FIRST RESPONSE® Early Result Pregnancy Test and FIRST RESPONSE® Digital Pregnancy Test uses advanced patented technology that enables them to deliver highly sensitive results. The test is able to detect total hCG, which is hCG and hCG-H combined, at lower levels than some other at-home pregnancy tests, which allows you to know sooner.

The FIRST RESPONSE® Early Result Pregnancy Test detects the pregnancy hormone five days before your expected period — with our most accurate results.1

In clinical research, FIRST RESPONSE® Early Result Pregnancy Test detected the hormone level in 62% of women five days before their expected period, in 78% of women four days before their expected period, in 87% of women three days before their expected period, in 98% of women two days before their expected period.

The FIRST RESPONSE® Digital Pregnancy Test detects the hCG hormone four days before your expected period.

In clinical research, FIRST RESPONSE® Digital Pregnancy Test detected the hormone level in 58% of women four days before their expected period, in 80% of women three days before their expected period, in 90% of women two days before their expected period, in 94% of women one day before their expected period.

Factors Affecting the Accuracy of At-Home Pregnancy Tests:
Today's tests are highly accurate and unlikely to yield false results. False positive results can occur due to the following:

  • There are remaining levels of hCG in your body due to a recent birth or miscarriage.
  • You are receiving injections of hCG to induce ovulation.
  • An ectopic pregnancy (a fertilized egg that implants outside of the uterus) has occurred. This may produce either a positive or negative result on a home pregnancy test and is a life-threatening condition. If you experience any abdominal pain or abnormal bleeding during the time when you think you might be pregnant, contact your health care provider immediately.
  • In a study of pre-, peri- and post-menopausal aged, non-pregnant women, about 0.2% of the women (over age 47) had very low levels of hCG that gave positive test results only when using a digital pregnancy test.


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1 First Response® can detect the pregnancy hormone as early as five days sooner than the day of your expected period.