Natural Cycles

Natural Cycles is a Swedish women's-health company behind the first birth-control application cleared by the US FDA (2018) and CE-marked in Europe as a Class IIb medical device. Its subscription app uses a proprietary temperature-based algorithm to identify fertile and non-fertile days from a user's daily basal body temperature, supporting both preventing and planning pregnancy as well as cycle, ovulation, and perimenopause tracking. Temperature is captured with a paired Bluetooth basal thermometer or through consumer wearables the app integrates with — Apple Watch, Oura Ring, and the NC B1 band. Natural Cycles publishes clinical research, an educational content library (CycleMatters), an e-commerce shop for thermometers and tests, and a public bug-bounty / responsible-disclosure program, but it does not expose a public developer API, developer portal, or OpenAPI. Backed by EQT Ventures.

Natural Cycles is profiled on the APIs.io network. Tagged areas include Company, Health Tech, Femtech, Women’s Health, and Fertility.

Natural Cycles’ developer surface includes engineering blog and 9 more developer resources.

🌐 Visit website 📡 Source on GitHub
13.6/100 minimal ▬ flat Agent 7/100 human only Full breakdown ↓
scored 2026-07-27 · rubric v0.5
0 APIs
CompanyHealth TechFemtechWomen's HealthFertilityBirth ControlCycle TrackingWearablesDigital HealthMedical Device

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 13.6/100 · minimal
Contract Quality 0.0 / 25
Developer Ergonomics 1.3 / 20
Commercial Clarity 4.2 / 20
Operational Transparency 1.4 / 13
Governance 0.0 / 12
Discoverability 6.8 / 10
Agent readiness — 7/100 · human only
Machine-Readable Contract 0 / 18
Agentic Access Contract 0 / 15
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 4 / 4
Consent & Bot Identity 3 / 3
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/natural-cycles: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Natural Cycles Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Natural Cycles Vulnerability Disclosure

security.txt · contact published

SECURITY

Resources

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

WellKnown
WellKnown

Access & Security 4

Authentication, authorization, and security posture

SecurityTxt
SecurityTxt
 Security
Security
 VulnerabilityDisclosure
VulnerabilityDisclosure
 DomainSecurity
DomainSecurity

Operate 1

Status, limits, changes, and where to get help

HelpCenter
HelpCenter

Commercial 2

Pricing, plans, and the legal terms of use

PrivacyPolicy
PrivacyPolicy
 TermsOfService
TermsOfService

Company 2

The organization behind the API

Website
Website
 Blog
Blog

Source (apis.yml)

apis.yml Raw ↑ 
aid: natural-cycles
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/natural-cycles.png
name: Natural Cycles
description: Natural Cycles is a Swedish women's-health company behind the first birth-control application cleared by the
  US FDA (2018) and CE-marked in Europe as a Class IIb medical device. Its subscription app uses a proprietary temperature-based
  algorithm to identify fertile and non-fertile days from a user's daily basal body temperature, supporting both preventing
  and planning pregnancy as well as cycle, ovulation, and perimenopause tracking. Temperature is captured with a paired Bluetooth
  basal thermometer or through consumer wearables the app integrates with — Apple Watch, Oura Ring, and the NC B1 band. Natural
  Cycles publishes clinical research, an educational content library (CycleMatters), an e-commerce shop for thermometers and
  tests, and a public bug-bounty / responsible-disclosure program, but it does not expose a public developer API, developer
  portal, or OpenAPI. Backed by EQT Ventures.
url: https://raw.githubusercontent.com/api-evangelist/natural-cycles/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- eqt-ventures
x-tier: stub
x-tier-reason: portfolio-lead
specificationVersion: '0.20'
created: '2026-07-17'
modified: '2026-07-20'
tags:
- Company
- Health Tech
- Femtech
- Women's Health
- Fertility
- Birth Control
- Cycle Tracking
- Wearables
- Digital Health
- Medical Device
apis: []
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: Website
  url: https://www.naturalcycles.com/
- type: HelpCenter
  url: https://www.naturalcycles.com/faqs
- type: Blog
  url: https://www.naturalcycles.com/cyclematters
- type: PrivacyPolicy
  url: https://www.naturalcycles.com/other/legal/privacy
- type: TermsOfService
  url: https://www.naturalcycles.com/other/legal/terms
- type: SecurityTxt
  url: well-known/natural-cycles-security.txt
- type: WellKnown
  url: well-known/natural-cycles-well-known.yml
- type: Security
  url: https://www.naturalcycles.com/other/legal/bug-bounty
- type: VulnerabilityDisclosure
  url: security/natural-cycles-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/natural-cycles-domain-security.yml
x-enrichment:
  date: '2026-07-20'
  status: enriched
  artifacts_added: 4
  pass: local-v1