Early Positive Pregnancy Tests: Are You Really Pregnant?

Early pregnancy tests are designed to tell whether you're pregnant five days before you miss your period. These sensitive tests aim to detect a hormone produced during pregnancy earlier than standard ones. But do they really work? Learn about these tests and how they compare to regular pregnancy tests.

How Is Pregnancy Detected?

First, a pregnancy test primer: Whether it's a blood test or a urine test done at a healthcare provider's office or in your bathroom, a pregnancy test is positive when it detects the hormone human chorionic gonadotropin (hCG)—a hormone produced by placental cells during pregnancy—in your system, according to John Hopkins Medicine.

The production of even a tiny amount of hCG means the fertilized egg has been implanted in the uterine lining.

At-Home Pregnancy Tests vs. Commercial Tests

The variance between at-home pregnancy tests is the amount of hCG they can detect, with early pregnancy tests detecting lower hormone levels.

"The commercial pregnancy tests range from 20 to 50 mIU/mL. Since hCG levels double every two to three days, some tests may detect hCG two to three days earlier—so there may be some benefit to using a more sensitive test," said Seth Guller, PhD, the director of the Gyn/Endocrine Laboratory at the Yale School of Medicine.

Guller added a surprising caveat: Any benefits of early pregnancy detection should be balanced by the fact that most pregnancies ending in miscarriage—or sudden pregnancy loss before 20 weeks—occur during the first seven weeks of pregnancy, according to MedlinePlus.

The Push for an Early Pregnancy Test

Knowing if you're pregnant early allows you to promptly make educated health and lifestyle changes that can increase the chance of delivering a healthy baby. This could include smoking cessation, getting vaccinations, and ensuring a healthy weight, according to the Centers for Disease Control and Prevention (CDC).

Charles Lockwood, MD, the chief of obstetrics and gynecology at Yale-New Haven Hospital, adds that "the risk of exposure to agents causing birth defects doesn't start until two weeks after conception."

There is no denying that trying to conceive is suspenseful. This is why a person might want to know about pregnancy as soon as possible—despite the emotional risk of learning about brief chemical pregnancies, which are miscarriages that occur within the first five weeks.

Are Early Pregnancy Tests Accurate?

There are biological factors that may affect the results of these tests. These super-sensitive tests claim to identify a pregnancy a whole week before a missed period, but embryos can fully implant (and start producing hCG) at different times. So, even if you're using the most sensitive test, your embryo may not immediately produce a positive pregnancy test. It may take several days.

"Embryo implantation is a process that unfolds over a number of days rather than a single event," said Hugh S. Taylor, MD, the chief of reproductive endocrinology and infertility at the Yale School of Medicine.

According to UCSF Health, it can take up to six days after fertilization for the embryo to become a blastocyst (mass of well-organized cells) and begin the implantation process.

"Embryos do grow at different rates; they can vary by about one day prior to implantation," Dr. Taylor said. "Pregnancy tests vary by the growth rate of the embryo and because of maternal body size and hydration status."

So every person may test positive on a different day, regardless of how fancy the test may be. Ultimately, it's up to you to decide if waiting to find out works for you or not.