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Observational Study of Natural Cycles for Contraception

This observational study is looking at how well the Natural Cycles app works to prevent pregnancy in everyday life. It's for women aged 18 to 35 who want to avoid pregnancy for about one year (13 menstrual cycles). You would use the Natural Cycles app as your only birth control method and regularly log information about sexual activity and test for pregnancy. The study aims to find out the pregnancy rate for all users and for those who follow the app's instructions perfectly. The main goal is to measure how effective Natural Cycles is at preventing pregnancy over one year.

Study design
This is an observational study aiming to enroll 2000 women. It is designed to evaluate the effectiveness of the Natural Cycles application under real-world conditions.
What's involved
You would use the Natural Cycles application for birth control for up to one year, log daily intercourse information, and complete a questionnaire at the beginning and end of your participation.
Compensation
Not stated in the trial record.
Follow-up
The primary endpoint measures contraceptive failure rate at 1 year (13 cycles).

AI-generated from the public study record. Only the study team can confirm whether you're eligible — confirm details with them before making decisions.

NCT07566793

Validation of Effectiveness on NaturalCycles Users

Recruiting
Not specifiedAges 18–35Observational
Natural Cycles
~2,000 participants
Updated 2026-07-01 on ClinicalTrials.gov
What's tested:Log daily intercourse informationNatural Cycles application

At a glance

Recruiting sites
1 of 1 listed site is recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
13-Cycles Cumulative Contraceptive Failure Rate
Measured over 1 year

Conditions

Contraception

Explore related trials

Contraception

Where it's being run

1 sites across 1 states
New York1

Study leadership

  • Eleonora Benhar, PhD · PRINCIPAL_INVESTIGATOR · Natural Cycles Nordic AB
  • Kristina Gemzell-Danielsson, PhD · PRINCIPAL_INVESTIGATOR · Karolinska Institutet

Who to contact

Agathe van Lamsweerde, MSc
[email protected]
201-431-6036
Email the study team

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Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

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.

Exclusion

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):

What this trial measures

  • 13-Cycles Cumulative Contraceptive Failure Rate1 year

    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.