Natural Family Planning (Sensiplan): How It Works and How Effective It Is
Clinical content by Elke Sedlmeier BA PgDip (NFP/FAM), Certified NFP/FAM Instructor. Last reviewed October 2026.
Key facts
- Natural family planning (NFP) identifies the fertile days of each cycle using waking temperature and cervical secretions.
- Taught and used correctly, the symptothermal Sensiplan method is more than 99% effective.
- NFP can be used to avoid pregnancy, to plan one, or to understand your cycle and spot problems.
- It takes three to six cycles to learn and works best with guidance from a trained instructor.
- We offer NFP teaching and diaphragm and cap fitting at our Twickenham clinic.
What is natural family planning?
Natural family planning (NFP), also called the fertility awareness method (FAM) or the symptothermal method, uses daily observations to identify the fertile and infertile days of the menstrual cycle. Unlike older calendar methods, it is based on signs from the current cycle rather than past cycle lengths, and uses two signs to double-check each other.
How does NFP work?
- Basal body temperature (BBT): your temperature on waking rises by at least 0.2°C after ovulation and stays raised until your next period.
- Cervical secretions: as ovulation approaches, rising oestrogen makes secretions wetter, clearer and more stretchy. After ovulation they change quickly.
- Cervical position (optional): the cervix rises, softens and opens slightly around ovulation.
A set of rules applied to these signs identifies the infertile days at the start of the cycle, the fertile window and the infertile days after ovulation.
How effective is NFP?
A large German study of the Sensiplan method, the method we teach, found 0.4 pregnancies per 100 women per year with correct use, comparable to the pill, and around 2 per 100 with typical use. Most pregnancies with typical use happen when couples knowingly have unprotected sex during the fertile window.
Benefits and drawbacks of NFP
- No hormones and no side effects
- Very low cost once learned
- Can be used to avoid or plan a pregnancy, and helps identify cycle problems such as absent ovulation or a short second half of the cycle
- Requires daily observation and three to six cycles to learn
- Requires abstaining or using a barrier method on fertile days, on average about 13 days a cycle
- Harder to use with very irregular cycles, for example when breastfeeding, approaching menopause or with PCOS
- Does not protect against sexually transmitted infections
Using NFP to get pregnant
Charting shows when you are most fertile and can confirm whether you are ovulating. The same German research found that couples who timed sex using their charts conceived faster: around 60% within three months and 81% within six months. Charts also help estimate when to take a pregnancy test and the likely due date.
How can we help?
- NFP teaching with our certified Sensiplan instructor, whether you want to avoid or plan a pregnancy.
- Diaphragm and cap fitting for the fertile days, if you prefer not to abstain. See our Contraception Choices page for more detail.
- Cycle assessment if your charts suggest irregular ovulation or other changes worth investigating.
Frequently asked questions
Is natural family planning reliable?
Taught well and used correctly, the symptothermal method is more than 99% effective. Effectiveness depends on following the rules consistently, which is why we recommend learning with a trained instructor.
Can I use NFP if my cycles are irregular?
Yes, because NFP is based on the signs in each cycle rather than its length. With very irregular cycles there may be longer fertile phases, and we can help you interpret your charts.
How long does it take to learn NFP?
Most women feel confident after three to six cycles with guidance.
Can NFP help me get pregnant?
Yes. Charting shows your fertile window, confirms whether you ovulate and can highlight problems early.
Book a consultation
To book, book an appointment online or call 020 3811 8778. Initial consultations last up to one hour at our clinic at 16 Bridle Lane, St Margaret’s, Twickenham TW1 3EE.