Prior miscarriage drives earlier, more frequent pregnancy testing

Findings from PRESTO (Pregnancy Study Online), a large North American preconception cohort study, shed light on factors driving the timing and frequency of pregnancy testing.¹

The analysis examined 20,458 pregnancy tests across 6569 unique participants enrolled between 2018 and 2024. Participants reported day-specific testing behavior spanning 4 days before through 4 days after their expected period, allowing investigators to characterize both the timing and frequency of testing and link those patterns to pregnancy detection outcomes.

Of the participants, 40.7% engaged in very early testing, defined as testing more than four days before their expected period. Testing intensity varied widely, with some participants testing only once and others testing daily.

Among participants who detected a pregnancy, very early testers were more than 5 times more likely to receive a negative test result before a positive one compared to those who waited until the day of their expected period (aRR 5.89; 95% CI, 4.73–7.33). Very early testers were also more than three times more likely to experience an initial positive result followed by a negative result, likely reflecting increased detection of very early pregnancy losses (aRR 3.80; 95% CI, 2.12–6.80).

"I believe that knowledge is power, and I hope that being able to weigh the benefits and drawbacks of different testing approaches empowers women to make informed decisions about testing that align with their values," said Alexandra Sundermann, MD, PhD, a study investigator.

Prior obstetric history emerged as a significant predictor of testing behavior. Participants with more children were more likely to be early testers. "We don't know exactly what was motivating this," Sundermann said, "but some of our investigators and I have hypothesized that maybe they recognize early symptoms of pregnancy before their counterparts who had not been pregnant before, and that motivated them to take an early test." Individuals with a history of miscarriage—particularly if the most recent pregnancy outcome was a loss—were more likely to be both very early and very frequent testers.

The findings carry implications for how pregnancy loss is defined and studied. Sundermann noted that very early losses may be biologically distinct from losses of confirmed intrauterine pregnancies. "It is reasonable to think that very early losses may have different mechanisms or a different set of risk factors than losses of confirmed intrauterine pregnancies with fetal cardiac activity confirmed," she said, "and therefore it makes sense to study them separately when we can."

When asked whether the data support formal guidance on pregnancy test timing, Sundermann was measured. "I do not think any guidelines should be born from one study alone," she said. The team's next step is to evaluate whether specific testing patterns are associated with post-cycle maternal anxiety or stress. "If we start to find strong ties with certain behaviors with post-cycle maternal mental health, then we might be able to start moving towards a recommendation."

Sundermann also noted that a forthcoming companion paper will present day-specific pregnancy test sensitivity estimates based on cycle length, along with a publicly available online tool to help individuals estimate the probability of a positive result based on their testing date.

Reference:

Sundermann AC, Jasper EA, Jukic AMZ, Rothman KJ, Wise LA. Pregnancy test use and timing of pregnancy detection in a prospective cohort of pregnancy planners. Obstet Gynecol. 2026;147(3):394-403. doi:10.1097/AOG.0000000000006157