How accurate are wearables at detecting ovulation?

A 2026 systematic review and network meta-analysis reported that wearable digital technology tracked the fertile window with a pooled accuracy of 0.88 (95% CI 0.86 to 0.90), a sensitivity of 0.79 and a specificity of 0.80. The authors graded the certainty of the evidence very low. Several device-specific validation studies are also funded or co-authored by the manufacturers.

What did the review of wearable ovulation detection find?

Shi et al., npj Digital Medicine 2026 searched eight databases through January 2025 and included 27 studies (6,244 participants, 14,288 menstrual cycles), 13 of which used wearables to track ovulation. The reference methods included urine hormone tests and ultrasound. Devices ranged from wristbands to rings. Accuracy was defined as the percent of cycles correctly classified.

Sensitivity was 0.79 (95% CI 0.70 to 0.87) and specificity 0.80 (95% CI 0.60 to 1.00), a wide interval. Accuracy was 0.90 (95% CI 0.88 to 0.93) for a window of plus or minus 2 days around ovulation and 0.88 (95% CI 0.84 to 0.92) for plus or minus 3 days. Detecting a temperature shift is a within-person comparison, the same logic as a personal baseline versus a population range.

Studies defined ovulation differently, the funnel plot was asymmetric (suggesting possible publication bias), and the evidence was downgraded to very low for risk of bias, inconsistency and imprecision. The authors describe the results as tentative support for pregnancy planning.

Who funds the studies of individual devices?

Often the manufacturer is involved. Wang et al., Human Reproduction 2025 tested Apple wrist-temperature algorithms in 260 participants. Apple funded the study, and several authors are Apple employees and shareholders. For completed cycles, the algorithm gave an estimate in 80.8% of eligible cycles, and 89.0% of those fell within 2 days of ovulation (urine LH tests).

In Niggli et al., Sensors 2023, on a wrist-worn device from Ava, one author was an employee and another sat on the advisory board. The retrospective algorithm identified 75.4% of fertile days.

Those figures cannot be ranked against each other, because outcomes and devices differ, as with a 2025 study of an armpit sensor reporting 98.6% accuracy, co-authored by the company’s chief executive. Company-linked studies can still be sound, but the metric shapes the headline number.

The bottom line

• A 2026 review of 27 studies pooled wearable accuracy at 0.88 (95% CI 0.86 to 0.90), with sensitivity 0.79 and specificity 0.80.
• Accuracy was 0.90 within plus or minus 2 days of ovulation and 0.88 within 3 days: a window, not a single day.
• Certainty was very low, and several individual device studies are manufacturer-funded or co-authored.