Study data highlight trade-offs of testing for pregnancy too soon

Home pregnancy testing behaviors vary widely among people trying to conceive, and very early testing carries important trade-offs between slightly earlier detection and a substantially higher likelihood of confusing or emotionally challenging results, according to new data from a large North American preconception cohort.¹

The analysis draws from PRESTO (Pregnancy Study Online), an ongoing preconception cohort study that follows individuals planning a pregnancy across North America. “PRESTO is a preconception cohort study that follows a group of individuals across North America who are planning a pregnancy,” said Alexandra C. Sundermann, MD, PhD, an assistant professor in the Division of Quantitative and Clinical Sciences and the Division of General Obstetrics & Gynecology in the Department of Obstetrics and Gynecology. “Before we can learn more about their behaviors and how it relates to pregnancy and pregnancy outcomes, in this analysis, specifically, we use the part of the survey where participants reported day-specific pregnancy testing behaviors.”

Using these data, investigators assessed the timing and frequency of home pregnancy testing as well as individual test results. “The specific analysis uses data from over 20,000 home pregnancy tests across 6500 individuals,” Sundermann said.

One of the study’s initial aims was descriptive. “We observed a wide variety of behaviors. Behaviors spanned from individuals testing every single day in the window that we looked at, compared to individuals who just tested a single time on the day of their expected period.”

Very early testing was common. “We found that over 40% of participants reported testing more than 4 days before their expected period, which is earlier than home pregnancy tests are expected to be reliably consistent,” Sundermann said. “The sensitivity of home pregnancy tests increases with each day after fertilization, and therefore very early testing increases the risk of having a negative test even when a pregnancy is present.”

Among participants who conceived, early testing was strongly associated with initial false-negative results. “As you may expect among the participants who did conceive, those who tested very early were more likely to have a negative test before they actually had that positive test that confirmed a pregnancy than individuals who waited,” she said. “Specifically in this analysis, those who tested more than 4 days before their expected period were over 5 times more likely to have those initial false negative tests.”

Early testing was also linked to a greater likelihood of detecting very early pregnancy losses. “Participants who tested very early were more than 3 times more likely to have an initial positive test that then was followed by a negative test later, which likely represents detections of very early losses that might have otherwise gone unrecognized,” Sundermann said.

Rather than issuing prescriptive guidance, the authors aimed to inform shared decision-making. “At this point, we intentionally left out any specific recommendations,” she said. “We acknowledge that individuals have different sets of values when it comes to how they approach pregnancy testing.”

For some, early knowledge outweighs the drawbacks. “For some individuals, detecting a pregnancy even 1 day earlier is worth having a handful of negative tests,” Sundermann said. For others, “Waiting until they will have a reliable positive test may spare them the emotional roller coaster of having a false negative.”

She also noted that marketing messages may shape expectations. “Much of marketing for pregnancy tests emphasized the benefits of earlier and earlier detection, and therefore, individuals might not be factoring in the potential downsides when making their decisions about when and how to test,” she said.

Importantly, the findings apply to pregnancy planners only. “We did not study individuals who might be testing for pregnancy because they desire not to be pregnant,” Sundermann said, noting that emotional responses to test results may differ in that population.

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