pregnancy complications

Testing Early for Pregnancy May Produce False Negative Results or Precede Early Pregnancy Loss 

A new study examining timing and frequency patterns for home pregnancy tests found that people who tested four or more days before the date of their first missed period had a substantially higher risk of receiving an initial negative test or a positive test that eventually resulted in a miscarriage.

Taking a pregnancy test can spark a range of emotions, from excitement and joy, to surprise and anxiety. For the most accurate results, it’s best to take these tests on the first day of a missed period.

Despite this recommendation, a new study led by researchers at the School of Public Health and Vanderbilt University Medical Center found that nearly 41 percent of pregnancy planners take “very early” pregnancy tests—at least four days before their expected period. 

And while very early pregnancy testing was linked to slightly earlier pregnancy detection, these test takers were more than five times more likely to receive an initial negative test result before a subsequent positive result if they were actually pregnant, compared to those who waited until the first day of expected menstruation to test. Very early test takers were also more than three times more likely to receive an initial positive test, followed by a negative one, likely reflecting the early detection of a pregnancy that will result in a miscarriage. 

The findings, which were published in the journal Obstetrics & Gynecology, suggest that very early pregnancy testing offers only a modest benefit in terms of how soon pregnancy is detected, says study senior author Lauren Wise, professor of epidemiology and principal investigator of Pregnancy Study Online (PRESTO), a web-based preconception cohort study that follows thousands of individuals ages 21-45 who are trying to conceive. Participants in the new study were enrolled in PRESTO.

Early pregnancy testing is associated with improved birth outcomes, but a test that is taken too early may not detect human chorionic gonadotropin (hCG), the hormone that is produced when a person is pregnant. 

“For pregnancy planners, there’s a tradeoff between getting information as early as possible and experiencing more uncertainty or emotional distress,” Wise says. “Some people prefer to know everything as early as they can, even if that information is ambiguous or emotionally challenging, while others may find repeated negative tests or early losses distressing.”

Neither approach is right or wrong, she adds—the key is understanding what information early testing can and can’t provide. Many test takers are unaware of the appropriate timing to take pregnancy tests because there is very little guidance on home pregnancy testing, which could be a result of the limited visit time doctors have with patients, perceptions that pregnancy testing is self-explanatory, and the fact that this clinical care for pregnancies typically begins after a positive test result, Wise says.

The study’s corresponding author is Alexandra Sundermann, assistant professor of obstetrics and gynecology in the Division of Quantitative and Clinical Sciences at Vanderbilt Health. 

To better understand pregnancy testing patterns and the outcomes, the research team analyzed the timing and frequency of more than 20,000 at-home pregnancy tests among 6,569 PRESTO participants from 2018 to 2024. 

These testing patterns varied widely. Only 26 percent of participants reported that they first tested for pregnancy on the day of their expected period or later. In terms of frequency, nearly 34 percent of participants tested only once, while almost 9 percent of participants tested every day for nine days (four days before the date of their expected period and four days afterwards), even after receiving a positive test result. Participants with multiple children were more likely to test sooner and more frequently than participants with no children. Those with a history of miscarriage were also more likely to test earlier and more often.

“Ultimately, these findings can help people choose a testing strategy that aligns with their emotional needs, prior experiences, and tolerance for uncertainty,” Wise says. 

The researchers are also exploring how to translate this insight into practical, patient-facing resources, including a possible online tool that would help people understand how timing, cycle characteristics, and testing behavior affect their chances of getting a reliable pregnancy test result.

“The goal of this tool would be informational, rather than diagnostic, by helping users understand probabilities and tradeoffs—not telling them exactly when to test,” says Wise.

At SPH, the study was coauthored by Kenneth Rothman, professor of epidemiology.