Fertility awareness methods (FAM): definition
Fertility awareness methods (FAM), also called natural family planning, are ways of estimating fertile days by tracking body signs such as basal body temperature, cervical mucus and cycle dates. They're used to plan pregnancy or, with careful training and strict rules, to avoid it. With typical use, about 2 to 23 in 100 people get pregnant each year, depending on the method.
The main methods
| Method | What you track |
|---|---|
| Calendar or rhythm | Past cycle lengths only |
| Standard Days | Fixed days 8 to 19, for 26 to 32 day cycles |
| Temperature | Daily basal body temperature |
| Cervical mucus (e.g. Billings) | Daily cervical mucus changes |
| Symptothermal | Temperature + mucus + calendar, sometimes cervix |
How effective is it?
Effectiveness depends heavily on the method and how consistently it's used. Methods that combine several signs and are taught by a trained educator work best. Calendar-only counting is the least reliable, because ovulation can move in any cycle, even if you're usually regular.
Calendar predictions and so-called safe days are not reliable contraception. Lulu is not a contraceptive and its fertile window estimates should never be used to avoid pregnancy. Talk to a clinician about effective methods.
Why it matters
FAM can be a great way to learn your body: when you ovulate, how long your luteal phase is, and how mood and energy follow. For conceiving, it helps time sex to the fertile window. It doesn't protect against STIs.
Read the balanced overview in the safe days explainer.
Frequently asked questions
Is the fertility awareness method reliable?
Combined methods taught by a trained educator and followed strictly can be fairly effective, but typical use has a meaningful failure rate. Calendar-only methods are the least reliable.
Can a period app be used as natural birth control?
Lulu can't and shouldn't. Its predictions are estimates for planning and understanding your cycle, not contraception.
Sources
This page is for information only and isn鈥檛 medical advice. If something worries you, please talk to a doctor.
Keep reading
Safe days calculator: why calendar safe days can't prevent pregnancyLooking for a safe days calculator? Here's why calendar safe days are unreliable as contraception, what the numbers say, and what works instead.What is the symptothermal method?The symptothermal method combines basal body temperature, cervical mucus and cycle dates to pinpoint the fertile window. How it works and its limits.What are "safe days"?"Safe days" are days of the cycle thought to carry a low chance of pregnancy. Why calendar-based safe days are unreliable, and what actually works.
Fertile window: definition and meaningThe fertile window is the six days each cycle when sex can lead to pregnancy. How it's worked out, when it falls, and why it isn't a contraceptive tool.Natural Cycles review: how it compares with Lulu (different jobs)An honest Natural Cycles review: hormone-free birth control cleared by the FDA, how it works, what it costs, and why Lulu does a different job entirely.