Natural Cycles
Swedish app created by physicist Elina Berglund, CE marked in 2017 and cleared by the FDA in 2018 as the first application approved for contraception in the United States. The algorithm reads basal body temperature, measured every morning with the supplied thermometer or pulled automatically from an Oura Ring or Apple Watch. Green days mean no protection needed, red days mean protection required. The company states 93 percent effectiveness with typical use and 98 percent with perfect use.
Works for disciplined users with a stable sleep routine who want a hormone free method with visible numbers. Night shifts, alcohol, fever and short nights distort temperature and produce long stretches of red days. Nothing here protects against infections, and the subscription is the only way in.
Pros
- FDA cleared for use as contraception
- Hormone free method with clear daily rules
- Syncs with Oura Ring and Apple Watch
- Thermometer included with the annual plan
- Separate postpartum and perimenopause modes
Cons
- Subscription only, no usable free tier
- Daily measurement discipline required
- Many red days after illness or bad sleep
- No protection against infections
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