New tool translates pregnancy test research into individualized patient counseling resource

A new evidence-based digital tool called Positively Pregnant offers ob-gyns a practical resource for counseling patients on pregnancy test reliability—translating research findings on cycle day and cycle length into individualized estimates that patients can access directly, according to Alexandra C. Sundermann, MD, PhD, whose research underpins the tool.

"Positively Pregnant gives ob-gyns a simple, easy-to-use, evidence-based resource to share with patients who are trying to get pregnant," Sundermann said. The tool addresses a gap she identified in available patient education: despite widespread early testing behavior among people trying to conceive, there has been little accessible, individualized information about how pregnancy test performance actually varies by the day of testing or real-world cycle characteristics.

Related: Positively Pregnant tool helps patients time home pregnancy testing

The research behind the tool confirmed that timing is the dominant driver of test sensitivity — but added a finding that was less expected. Cycle length independently affects the probability of a positive result for the same day of testing relative to an expected period. Specifically, people with shorter cycles were less likely to obtain a positive result than those with longer cycles when testing on the same day pre-period. "Three days before an expected period, a pregnancy test would have a sensitivity of about 70% for someone with a regular 22-day cycle, compared to 88% for someone with a 34-day cycle," Sundermann said.

Those findings are now embedded in the tool as individualized sensitivity estimates. Rather than offering patients a single population-level probability, Positively Pregnant allows them to input their own timing and cycle characteristics to understand what a negative test result actually means for them on a given day. "Instead of giving patients a one-size-fits-all answer about pregnancy test reliability, they can better understand test performance based on their own timing and cycle characteristics," Sundermann said.

For ob-gyns, the clinical value is in supporting more nuanced counseling conversations around early testing — particularly for patients who test before their expected period and receive a negative result that may not reflect the true status of the pregnancy.