The science behind the Modern Fertility Pregnancy Test

Sharon Briggs, PhD - Contributor Avatar

Reviewed by Sharon Briggs, PhD, 

Written by Health Guide Team 

Sharon Briggs, PhD - Contributor Avatar

Reviewed by Sharon Briggs, PhD, 

Written by Health Guide Team 

last updated: Jun 17, 2020

4 min read

We’ve been hard at work developing an affordable, clinically sound pregnancy test — and it’s finally here.

The Modern Fertility Pregnancy Test is 99% accurate from the day of your missed period 1 and more affordable 2 as top-selling tests in stores.

You can test  pregnancy early – up to 6 days before your missed period.Here, we’ll explain exactly what happens in your body during early pregnancy and how the Modern Fertility Pregnancy Test works.

Modern Fertility

Get proactive about your reproductive health

What are pregnancy hormones and what do they do?

Let's get back to basics for a moment. During ovulation, an egg is released from a fully matured follicle into the fallopian tube and remains there for 12-24 hours. If sperm is waiting there or comes along during that time and successfully fertilizes the egg, the whole package — now called an embryo — makes its way to the uterine lining and takes root. That's when the surrounding cells start generating a hormone called human chorionic gonadotropin, or hCG.

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Average hCG in early pregnancy

What does hCG do?

  • hCG protects the developing fetus from your body's immune system (which considers it an invader and wants to eradicate it).

  • It ensures that the corpus luteum, the remains of the follicle that released the mature egg, emits high levels of estrogen and progesterone — hormones that are vital for maintaining both the uterine lining and the pregnancy itself.

  • Finally, it’s the hormone our pregnancy test looks for. hCG levels multiply in the body super quickly after implantation — making it a great indicator of early pregnancy. Early on in pregnancy, hCG levels increase roughly 50% every day!

How does the Modern Fertility Pregnancy Test and free app work?

Our test looks for the presence of hCG in your urine. If it's there, hCG joins up with anti-hCG proteins in the test — that's what triggers the appearance of a positive test line. hCG needs to accumulate in your urine in order to be able to be detected, so while the test can't tell you whether or not you're pregnant right after sex, it can detect hCG in super low amounts (10 milli-international units per milliliter, or mIU/mL).

That’s why getting a negative test result doesn’t always mean you’re not pregnant — it could just mean that there isn't a detectable amount of hCG in your urine yet. If that happens, waiting 48 hours and then testing again could get you a different result. That said, we recommend testing on the day of your missed period for the highest level of accuracy — and most doctors agree.

How do you take Modern Fertility Pregnancy Test?

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Modern Fertility Pregnancy Test

Here's what to know before you pee on that stick:

  • Test first thing in the morning, when your urine is the most concentrated.

  • Let the test rest for 5 minutes after you pee on the absorbent tip.

  • Don't wait more than 10 minutes to look at the result, as the result will be invalid.

  • One line indicates that you're not pregnant (though it could also mean there's not enough hCG in the urine yet).

  • If there are two lines visible, it's positive — but if the lines are faint, we recommend testing again after 48 hours later.

  • If there's no line after 5 minutes, you might not have used enough urine — or the test might be invalid. Try again with another test.

  • Any and all results you get should be confirmed and discussed with your doctor.

Now, you can stock your medicine cabinet with a test you know will help you answer that big question sooner and with more certainty — whether you’re trying for kids, or just want to be prepared.

Is there anything that can affect the accuracy of a pregnancy test result?

Pregnancy tests can be delicate, so make sure you follow the instructions that come with the test. In addition, the outcome of your test can be impacted by certain things, such as:

  • Drinking a ton of water before you test (as it dilutes your urine and can result in a false negative)

  • An expired test (as it won't give you an accurate result)

  • Fertility medication that contain hCG (as the excess can trigger a false positive)

  • A recent miscarriage or a chemical pregnancy (you could get a false positive due to the remaining hCG in your body)

It's time to modernize reproductive health

Yes, we’re hormone nerds — and we’re proud of it. Our mission is to make personalized fertility information more accessible. In addition to our Pregnancy Test, we also offer other products and digital tools, including:

  • The Modern Fertility Ovulation Test, which helps you pinpoint your luteinizing hormone (LH) levels to predict your 2 most fertile days. With our test, you’ll get more insight than just a positive or negative result — you’ll be able to see your LH change daily and track low, high, or peak levels. This is key for understanding whether you're in your fertile window and approaching ovulation (when you have the highest chances of pregnancy).

  • The Modern Fertility Hormone Test, which measures the same fertility hormones that a doctor would test in a fertility clinic (for a fraction of the price) and helps you understand how your fertility is changing over time. Our test gives you insight into the number of eggs you have and can help you identify red-flag issues — like PCOS or thyroid conditions — that could affect your reproductive health down the line.

  • Our Modern Fertility Prenatal Multivitamin helps you prep your body now for pregnancy whenever. It's designed to support your body before, during, and after pregnancy with 12 essential, doctor-backed nutrients. It comes in a sustainable monthly subscription with a (beautifully blue!) reusable glass jar — meaning no more forgotten refills or empty plastic bottles.

We believe that understanding your hormones is the key to understanding your fertility and reproductive health. Our at-home tests give you the info you need about your body to get proactive about all things fertility.


1 99% accurate at detecting typical pregnancy hormone levels from the first day of your missed period. However, hormone levels may vary — and some pregnant people with ovaries may not have detectable amounts of pregnancy hormone in their urine on the first day of their missed period or may have miscalculated the first day of their missed period. If you receive a negative result but believe you may be pregnant, test again in 48 hours with an early morning (first) urine specimen or consult with your doctor.

2 Based on the average price of the top 5 pregnancy tests in retail stores by sales volume. Source: Nielsen retail sales data in 2021.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

June 17, 2020

Written by

Sharon Briggs, PhD

Fact checked by

Health Guide Team

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