When to Take a Pregnancy Test

Understanding How Pregnancy Tests Really Work

When Is a Pregnancy Test Most Accurate?
© Verywell, 2017.

For many women, the decision to when to take a pregnancy test is a major source of anxiety. If you're trying to get pregnant, you may spend the entire two-week wait debating whether to "pee on a stick" early or wait a little longer. If you're trying to conceive, you're probably dying to know if this month will be the month you get your positive test result. You also may feel tempted to take the test before your period is late, especially if you have early pregnancy signs.

But taking the test early may come up negative, even if you are pregnant. How do you decide when to resist and when the right time to take a test is?

The Best Time to Take a Pregnancy Test

The best time to take a pregnancy test is after your period is late. This will help you avoid false negatives and the false positives of very early miscarriages. If you're not already keeping a fertility calendar, proper pregnancy test timing is a good reason to start one.

If your cycles are irregular or you don’t chart your cycles, don't take a test until you’ve passed the longest menstrual cycle you usually have. For example, if your cycles range from 30 to 36 days, the best time to take a test would be day 37 or later.

Something else to consider is whether you know if your period is even late.  According to the FDA’s website, out of every 100 women, 10 to 20 will not get a positive pregnancy test result on the day they think is just after their missed period, even if they are pregnant.

Even tests labeled for early pregnancy detection can't accurately detect a pregnancy before your period is late.

How Do Pregnancy Tests Work, Anyway?

Knowing how these tests work can help you understand when to take them.  

The tests detect the pregnancy hormone, human chorionic gonadotropin (hCG), in your urine.

 Some tests also detect a variation of this hormone, known as hyperglycosylated hCG (H-hCG). The regular hCG is produced only after an embryo implants into the endometrium. H-hCG begins to be released earlier, sometime after fertilization.

    An at-home pregnancy test can't measure the exact amount of pregnancy hormone in your urine. What it can do is detect whether a minimum amount is present. Getting a negative pregnancy test result doesn't mean your urine doesn't contain hCG. It just means it doesn't contain enough to trigger a positive result.

    When pregnancy tests tell you how much hormone they detect, they usually tell you how much hCG the test requires. A woman’s level of H-hCG, though, is typically higher than hCG. If a pregnancy test detects H-hCG, you’re more likely to get a positive result early. If a pregnancy test is not sensitive to H-hCG, and only detects regular hCG, getting an early positive result is less likely. Most pregnancy tests on the market are not great at detecting H-hCG.

      Understanding How Early Result Pregnancy Tests Work

      Early results tests promise results three or four days before your missed period. These tests assume a 14-day luteal phase, which is the time between ovulation and when you get your period.

      The problem is that you may have a shorter or longer luteal phase.

      If your luteal phase is usually 12 days, four days before your missed period would be nine days after ovulation. That's way too early to test. For you, taking the test four days before your missed period would be pointless.

      If you have a luteal phase of 15 days, four days before your missed period is 12 days after ovulation. You still may not have enough hormone that early, but you’ve got a better chance than someone with a shorter luteal phase.

      If you’ve have had an hCG trigger shot like Ovidrel, then you should not take an early pregnancy test.

      An early test may detect the remains of the fertility medication.

        But What About the 99 Percent Accuracy?

        If you read the instructions carefully, this test promises 99 percent accuracy on the day of your missed period—not for early results.  If you expect your period on Wednesday, Thursday would be the day of your missed period.

        Surprisingly, these promises of 99 percent accuracy may not be true. In research studies, where they compared how much hCG the test claimed to detect and how much it actually detected, the tests were only 46 percent to 89 percent accurate. In one study, pregnancy tests indicated a positive result only 80 percent of the time on day 28 of the woman’s menstrual cycle.

          Pros and Cons of Taking a Pregnancy Test Early

          Are you feeling tempted to take a test before your period is late? Consider the pros and cons.

          Pros:

          Cons:

          • Good chance of getting a false-negative
          • Feelings of disappointment if you get a negative result
          • Loss of cash (Tests cost $1 to $18 per test)
          • If positive, possibility of detecting an early miscarriage you may have missed if you hadn’t tested early
          • Not accurate with hCG trigger shots such as Ovidrel

          The Best Early Pregnancy Test & What Day You're Most Likely to Get Results

          Let's say you want to take an early test, despite the possible downsides. Which test should you use?

          According to the research, the best early pregnancy test on the market now is The First Response Early Result, or, as it's sometimes abbreviated on fertility forums, the FRER. This is their manual test, not the digital one, which is actually slightly less accurate.

          This is the only pregnancy test that has clearance from the FDA to say it can detect pregnancy hormones six days before your missed period. That is five days before your period is due.

          How accurate is it that early? Here are the results from one study:

          • One day past your expected period: detected 100 percent of pregnancies
          • On the day of your expected period: 96 percent of pregnancies detected
          • On the day before your expected period: 93 percent of pregnancies detected
          • Two days before your expected period: 81 percent of pregnancies detected
          • Three days before your expected period: 68 percent of pregnancies detected
          • Four days before your expected period: 42 percent of pregnancies detected
          • Five days before your expected period: 33 percent of pregnancies detected
          • Six days before your expected period: 25 percent of pregnancies detected

          How do these statistics compare to other brands? According to this same study, E.P.T manual tests (not the digital one) detected only 53 percent of pregnancies on the day of a woman's expected period. The First Response Early Results test was more accurate three days before a woman's expected period than E.P.T.'s test was on the day of the expected period.

            A Word From Verywell

            The best time to take a pregnancy test is the day after your expected period. However, when you're anxious to see results, it's understandable if you are tempted to test earlier.

            Before you reach for that early pregnancy test, carefully consider how you'll feel if the results are negative. If a negative test doesn't bother you, and you have the cash to spend on pregnancy tests, go ahead. If a negative result is going to make your heart ache or if you’d rather not waste money on extra tests, then wait until your period is late.

            Source:

            Cole LA. The utility of six over-the-counter (home) pregnancy tests. Clin Chem Lab Med. 2011 Aug;49(8):1317-22. doi: 10.1515/CCLM.2011.211.

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