Very early home pregnancy testing modestly advances detection but substantially increases false negatives and detection of very early pregnancy losses, according to a recent study.
In a North American prospective prepregnancy cohort study conducted from 2018 to 2024, investigators analyzed 20,458 pregnancy tests reported by 6569 pregnancy planners. Participants provided day-specific testing information from 4 days before to 4 days after their expected menstruation. The study examined determinants of testing behavior, timing of pregnancy detection, and risks associated with early testing.1
Overall, 40.7% of participants engaged in very early testing, defined as more than 4 days before the expected period. Testing intensity varied substantially, ranging from a single test to daily testing. Among those who ultimately detected pregnancy, very early testers were nearly 6 times more likely than those who waited until the expected day of menstruation to experience a negative test before a positive result (adjusted risk ratio [aRR] 5.89; 95% CI, 4.73-7.33). They were also more than three times as likely to report a positive test followed by a negative test (aRR 3.80; 95% CI, 2.12-6.80), a pattern suggestive of very early pregnancy loss.
Study author 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 at Vanderbilt University Medical Center in Nashville, Tennessee, noted that approximately 2% of participants reported a positive test followed by a negative test. “We expect mostly [that this] represents these very, very early losses,” she said, while acknowledging that assay variability or user interpretation could contribute in some cases. However, she emphasized that increasingly sensitive home tests are likely changing what patients experience. “As pregnancy test results become increasingly sensitive, the natural consequence is that individuals will be detecting these early losses at home with increasing frequency.”
She pointed to earlier research demonstrating that when highly sensitive assays were used to test daily urine samples, early pregnancy loss rates approached 1 in 3 conceptions—far higher than the commonly cited miscarriage risk of roughly 1 in 6 or 1 in 7. Historically, most of these early losses went unrecognized.
The benefit of early testing, meanwhile, was modest. Compared with individuals who waited until the expected period or later, very early testers detected pregnancy about 4 days sooner on average. But compared with those testing 1 to 3 days before the expected period, detection occurred only about 1 day earlier. “This group that tested 1 to 3 days before their expected period were much less likely to have those false negatives or those positive followed by negative tests,” Sundermann said.
She added that the emotional consequences may outweigh the limited timing advantage. “Most patients experience this as a true loss,” she said, noting that positive-then-negative results often generate anxiety and clinical questions. “These experiences generate a lot of clinical questions for which we don’t really have good answers… it’s really hard to tell patients that we just simply don’t know.”
The findings highlight the need for anticipatory counseling about testing timing, test sensitivity, and the psychological implications of detecting transient pregnancies.
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
