This form of contraception is said to be between 95-98% efficient. You must be a female who knows their body inside out, and knows their menstrual cycle backwards. Basically you cannot have sex (unless you use other forms of contraception) just before, during and after ovulation. This is about a one to two week time frame. So as you can see this method has it's disadvantages.
How does it work?
You have to know your menstrual cycle well. And it must be regular. It is only around the time of ovulation that you can fall pregnant. Therefore by using this form of contraception you must not have unprotected sex around the time of ovulation. A female usually ovulates between her 14-16th days before the next cycle. The ovum (the female egg) lives for around 72 hours. Therefore when you know when you are ovulating you cannot safely have sex without risk of pregnancy until at least 3 days after ovulation. But that's not all, the life of a sperm is about 72 hours also, so you cannot have sex safely 72 hours prior to ovulation, as the sperm can fertilise the egg once you ovulate three days later. Therefore on average, a female is usually unsafe to have sex between her 11 and 18 days before her next period (or what is referred to as her cycle). Please remember that this is only estimation, and may be extremely inaccurate for your cycle.
This form of contraception is best used for couples who are not going to be too distressed if an unplanned pregnancy occurs. As with this form of contraception you must strictly follow the rules and watch for the signs of ovulation very carefully.
There is a system that can be used to help you know when you are about to ovulate. The cycle of a female begins on the first day of her menstrual period (the first day of bleeding). Therefore it is important a diary is kept for the whole month, starting with the first day you bleed. This diary needs to be kept for 12 cycles, so that you are able to see if your periods are regular and on average how many days in your cycle. The system of working out your unsafe days is rather difficult to understand, but if you are keen to use this method, here's what you need to do.
To allow for variation in the length of your cycle you must:
Work out the first unsafe day of your cycle.
This can be done by subtracting 18 days from the number of the shortest cycle within the last 12 periods.
Eg. The shortest cycle was 26 days (in 12 cycles) subtract 18 = 8.
Work out your last safe day of your cycle.
This can be done by subtracting 11 days from the number of the longest cycles within the last 12 periods.
Eg. The longest cycle was 32 days (in 12 cycles) subtract 11 = 21.
In brief, if the shortest cycle in 12 cycles was 26 days, and the longest one was 32 days, then the calculation will be:
Shortest day = 26, minus 18 days = 8
Longest day = 32, minus 11 days = 21
Therefore your unsafe times are between 8 and 21 days.
This leaves you with 13 unsafe days (21 minus 8 = 13).
It is during these 13 days that you must be careful not to have unprotected sex and use other methods of contraception.
- Remember, this is an example, it is up to you to work out your own unsafe days
There are ways to reduce this gap.
When a female is about to ovulate her temperature will rise slightly. So during those 12 cycles where you are working out the length of each cycle, you need to take your temperature every day. You will find an increase in your temperature as you ovulate (if only by half a degree); this is due to progesterone rising in the body, which is helping to release of the unfertilised egg.
The other sign is that your natural mucous from your vagina will change as you begin to ovulate. Normal vaginal secretions should be thick and slightly sticky. But increasing estrogens in the body that rise with ovulation cause the secretions to become more clear and watery. This is due to the natural way the body prepares for implantion of a fertilised egg, it causes the environment to be more appropriate for the movement of the ovum and sperm so that they may fertilise and implant in the uterus.
So an elevated temperature and a change in your natural vaginal secretions are other helpful ways to know when your body is preparing to ovulate.
There are products being trialed at the moment that can be used to test for ovulation, however they are not easily accessible as yet. But in the future, they will be great to detect when ovulation is going to occur.
As you can see, this natural method of contraception is a difficult one to achieve. If the rules are followed correctly, chances of pregnancy are low, but you must ensure that you use another form of contraception during your unsafe days. This kind of contraceptive method is one that is typically used for couples who have been together for a while, as there is no barrier against HIV and STDs, and trusting your partner (and yourself) must be a consideration. It is also a method where you and your partner are both aware of how this works, as he needs to understand why there are days you cannot have sex without protection. If you choose this method, please discuss it in more detail with your doctor for any other things you may need to know, as this is only a brief outline of the 'natural method.'
- Louise Ganey (RN)