Contraception: natural family planning
What is natural family planning?
Natural family planning is a form of birth control that involves abstaining from having sex during the times that you are most likely to become pregnant. It is also sometimes referred to as the fertility awareness-based method or periodic abstinence.
You should always check with your doctor before using this method of contraception, as it is not suitable or reliable for all women.
How does it work?
The natural family planning/fertility awareness method works by determining your fertile days (days during your menstrual cycle you are most likely to get pregnant) and abstaining from sex on those days. Alternatively, you can use a different form of contraception (such as condoms) on your fertile days.
Working out when in your cycle you are fertile can be done by observing changes in your basal body temperature (BBT) and/or cervical mucus. Some people use the calendar method (rhythm method), where you chart your menstrual cycle on a calendar. The sympto-thermal method involves combining these 3 methods. (See below for details.)
When are the fertile days?
A woman’s fertile days are around the time of ovulation (the release of an egg from one of the ovaries). After ovulation, eggs survive for about 24 hours. Because sperm can survive for as long as 5-7 days (the average is 2-3 days) in the female reproductive system, most women are considered fertile for about 5 days before and 2 days after ovulation. Some women will need longer periods of abstinence due to variability in menstrual cycles.
It’s recommended that you talk to your GP (general practitioner) or a health professional at a Family Planning Clinic before relying on this method of contraception. It takes training and several cycles to accurately work out when in your cycle you are fertile.
How effective are fertility awareness methods as contraception?
The effectiveness of natural planning/fertility awareness methods can vary enormously, depending on the particular technique used, and the commitment to the method.
Effectiveness can be measured for perfect use and typical use. The following figures are estimates based on limited studies.
- Perfect use is when instructions are followed precisely. Failures during perfect use represent failure of the method itself. Reported failure rates for perfect use of fertility awareness methods range from one per cent to 5 per cent.
- Typical use is what tends to happen in reality. Typical use failures include failures due to incorrect use of the method. Typical use failure rates for fertility awareness methods are about 15-24 per cent.
When used for a year by 100 women, the different methods below have the following typical use failure rates.
|Typical use failure rates*|
|Temperature method||14-25 pregnancies|
|Cervical mucus method||11-34 pregnancies|
|Sympto-thermal method||2-8 pregnancies|
|Calendar method||11-14 pregnancies|
|*Figures are estimates based on limited studies.|
Failures are due to either having sex on a fertile day or inaccurate prediction of the fertile phase.
Advantages of natural family planning
Some of the advantages of natural family planning include the following:
- this method doesn’t require medicines, chemicals or devices;
- it is inexpensive;
- women using this method become very aware of their reproductive cycles, which can be an advantage if and when they decide they would like to become pregnant;
- fits in with most cultural and religious beliefs.
Disadvantages of natural family planning
Some of the disadvantages of natural family planning include the following:
- women must be highly motivated to use this method of contraception correctly.
- it requires extensive instruction and many steps to accurately predict ovulation and the fertile phase.
- it may result in periods of sexual frustration during periods of abstinence.
- this method of contraception does not offer protection against sexually transmitted infections (STIs).
- accurately predicting fertile days can be difficult as the length of menstrual cycles and the day of ovulation may vary each month.
- natural family planning may not be suitable for some women, including those with irregular periods or those approaching menopause.
- some indicators of fertility can be altered by illness and stress.
- in practice, it is often not as reliable as other methods of birth control.
What are the different types of natural family planning?
There are several ways to monitor your menstrual cycle for natural family planning. Regardless of the method you use, you can record and track your observations using a fertility chart or smartphone app. But remember to check with a healthcare professional before relying on any fertility apps as your sole method of contraception.
A woman’s body temperature rises slightly after ovulation and stays elevated until her period starts. So, by accurately measuring your temperature you can track ovulation and your fertile days.
To use the temperature method, you should take your basal body temperature (BBT) at the same time every day upon waking, before getting out of bed, eating or drinking. You can take your temperature with a special basal or ovulation thermometer that can give an accurate measurement to within one-tenth of a degree (0.1 Celsius).
There are several factors that can skew your temperature recordings:
- sleeping in;
- having too little sleep;
- drinking alcohol the night before;
- shift work;
- travel and time zone differences;
- certain medicines; and
- using an electric blanket.
If you chart your daily temperature correctly, you will notice that after ovulation your BBT will rise by 0.2-0.5 degrees Celsius. Once you have recorded temperature rises for 3 consecutive days (all of which exceed the previous 6 recordings), it’s likely that you are no longer in the fertile phase. So, it’s considered safe to have sex from this time until your period starts (i.e. only for about 12 out of 28 days each cycle).
Cervical mucus method
To use the cervical mucus method, you must learn to distinguish between your fertile and infertile days on the basis of the type of mucus (secretions) being made in your cervix.
During the first part of your cycle (immediately after your period) you may not notice much in the way of vaginal discharge. But around the time of ovulation (fertile phase), your body produces clear, stretchy, slippery mucus. After ovulation there is usually thicker, cloudier mucus before your period starts and the cycle starts again. You should mark these changes in mucus on a chart, indicating your fertile peak (last day of the slippery mucus).
When trying to avoid pregnancy, you should NOT have sex (or use another method of contraception):
- when you have slippery mucus;
- for about 3 days before you start getting slippery mucus; and
- until 3 days after the slippery mucus has peaked.
You should also avoid sex (or use another method of contraception) during your period, especially if you have a short cycle.
The cervical mucus method is not reliable for women who have abnormal vaginal bleeding or inflammation of the cervix or vagina. Cervical mucus signs are also difficult to read in women taking certain medicines (e.g. antibiotics, antihistamines, thyroid medicines) that can change the nature of vaginal secretions.
Calendar (rhythm) method
This method is based on the assumption that ovulation takes place 12-16 days before your period starts. Knowing the length of your last 6 menstrual cycles, you can use this information to roughly predict when you should abstain from sex. In general, there is a 12 day fertile window where you need to abstain from having sex.
This method is generally not recommended on its own because of its unreliability, especially if you have irregular menstrual cycles. It’s also only recommended for women with cycles between 27 and 32 days.
This method uses a combination of the above 3 techniques, making it the most accurate form of natural family planning.
Where to get more information on fertility awareness
Talk to your GP (general practitioner) about whether natural family planning/fertility awareness methods are appropriate for you and to get further information, education and training on the various methods. You could also visit your nearest Family Planning Clinic.
There are many smartphone apps available that can help your track your cycles. Make sure to check with a health professional before relying on apps and other devices for contraception.
Last Reviewed: 24/10/2019
1. Family Planning Victoria. Natural family planning (updated 28 Jun 2018). https://www.fpv.org.au/for-you/i-dont-want-to-get-pregnant/contraception-without-hormones/natural-family-planning (accessed Oct 2019).
2. American College of Obstetricians and Gynecologists. Fertility awareness-based methods of family planning (updated Jan 2019). https://www.acog.org/Patients/FAQs/Fertility-Awareness-Based-Methods-of-Family-Planning (accessed Oct 2019).
3. Fertility awareness based methods for pregnancy prevention. BMJ 2019;366:l4245. https://www.bmj.com/content/366/bmj.l4245
4. BMJ Best Practice. Contraception (updated Jun 2019; reviewed Sep 2019). https://bestpractice.bmj.com/topics/en-gb/418 (accessed Oct 2019).
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