Validation of Effectiveness on NaturalCycles Users

NCT07566793 | Recruiting FDA Device

• 1 other identifier: RES-2025-001
• Study Type: observational
• Target: 2,000
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this observational study is to measure the effectiveness of the Natural Cycles digital birth control application at preventing pregnancy in sexually active women aged 18 to 35 with no known history of infertility. The main questions it aims to answer are:

• What is the pregnancy rate of the application over one year, for all users?
• What is the pregnancy rate of the application over one year, for users who follow the application's instructions perfectly? Participants will:
• Use the Natural Cycles application for birth control for up to one year.
• Log information about daily sexual activity in the app.
• Complete a questionnaire at the beginning and end of their participation.
• Perform urine pregnancy tests (provided by mail) upon entry to the study, at the start of every cycle during the study, and upon exit from the study.

Conditions

Contraception

Outcome Measures

Primary Outcomes (1)

• 13-Cycles Cumulative Contraceptive Failure Rate

  The cumulative contraceptive failure rate in Typical Use and Perfect Use will be calculated using Kaplan-Meier survival analysis. This represents the probability of becoming pregnant within the first year of typical or perfect use of the Natural Cycles app. A confirmed pregnancy, identified through a positive urine pregnancy test, will be considered an event.

  1 year

Secondary Outcomes (4)

• Pearl Index (PI)

  1 year

• One-year study continuation rate

  1 year

• One-year product continuation rate

  1 year

• Participant satisfaction ratings

  At study exit, at most 1 year after entry to study.

Study Arms (1)

NC° Users Participating in Study

An individual who has recently registered to the Natural Cycles app will be screened based on the information routinely collected at registration and invited to the study if they meet specific screening criteria. After informed consent, the onboarding survey will explicitly verify further inclusion and exclusion criteria with participants.

Behavioral: Log daily intercourse information; Device: Natural Cycles application

Interventions

Log daily intercourse information BEHAVIORAL

For the duration of their participation in the study, participants will use the contraceptive app as usual but will be prompted to diligently log daily intercourse information and to regularly test for pregnancy. Upon exiting the study for any reason, all participants will complete a urine pregnancy test and an online Exit Questionnaire.

NC° Users Participating in Study

Natural Cycles application DEVICE

Users will receive daily fertility status from Natural Cycles application

NC° Users Participating in Study

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: female
• Healthy Volunteers: No
• Age Groups: Adult (18-64)
• Sampling Method: Non-Probability Sample

Study Population

New Natural Cycles application users living in the United States

You may qualify if:

• Wants to avoid pregnancy for 13 cycles.
• Is willing to rely solely on Natural Cycles as their sole contraception method for 13 cycles.
• Is not currently using permanent contraceptive methods, such as sterilization (of either the user or their partner), or hormonal methods, such as the hormonal contraceptive implant or IUD.
• Has an intact uterus, both ovaries and both fallopian tubes to the best of their knowledge.
• Has an average cycle length between 21 and 35 days. The user anticipates heterosexual intercourse at least once a month in the next year.
• Is willing to enter data on a daily basis and perform pregnancy tests as requested by protocol.
• Is willing to complete a satisfaction survey at the end of her study participation.

You may not qualify if:

• Has EU-citizenship
• Has had a Depo-Provera injection in the last 10 months or has had less than three consecutive, spontaneous menstrual cycles since their last injection.
• Has had less than three consecutive, spontaneous menstrual cycles after removing a hormonal implant.
• Has had less than three consecutive, spontaneous menstrual cycles after the end of a pregnancy.
• Has had less than three consecutive, spontaneous menstrual cycles since she last breastfed.
• Has (or partner has) known fertility issues, such as infertility and sterilization, or have been advised by a healthcare professional that they may have difficulty conceiving for any reason.
• Has a medical condition possibly impacting fertility, i.e. endometriosis, a history of Pelvic Inflammatory Disease (PID), significant uterine fibroids or adenomyosis, or another diagnosed medical condition that they have been told affects fertility.
• Is regularly taking one of the following prescribed pharmaceutical medications known to be teratogenic (i.e., a medication that can cause birth defects):
• Isotretinoin (like Accutane, Absorica, Claravis, or Myorisan) for severe acne Valproic acid or divalproex sodium (like Depakote, Depakene, or Topamax) for seizures (epilepsy), migraines, or bipolar disorder Methotrexate (Trexall, Rheumatrex) or leflunomide (Arava) for autoimmune conditions ACE Inhibitors (like Lisinopril, Enalapril) or Angiotensin II Receptor Blockers (ARBs) (like Losartan, Valsartan) for high blood pressure or heart conditions Warfarin (Coumadin, Jantoven) for blood clot prevention

Sponsors & Collaborators

• Natural Cycles: lead

Study Sites (1)

Natural Cycles USA Corp

New York, New York, 10036, United States

RECRUITING

Study Officials

• Eleonora Benhar, PhD

  Natural Cycles Nordic AB

  PRINCIPAL INVESTIGATOR

• Kristina Gemzell-Danielsson, PhD

  Karolinska Institutet

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Agathe van Lamsweerde, MSc

CONTACT

201-431-6036; venus_study@naturalcycles.com

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: November 18, 2025
• First Posted: May 5, 2026
• Study Start: April 28, 2025
• Primary Completion (Estimated): December 1, 2027
• Study Completion (Estimated): December 1, 2027
• Last Updated: May 8, 2026

Record last verified: 2026-05

Locations

US (1)