Contraception provides a high degree of protection against unwanted pregnancy, although the effectiveness of different methods varies. For each method described here, effectiveness is defined as the number of women per hundred per year who do not become pregnant while using it and is expressed as a percentage. For most methods, apart from the IUD, your doctor will need to explain how to use them so that they are effective. It may take some time to learn how to use a diaphragm, a cap, or natural methods, and they are not suitable for times when you need contraception immediately. A condom is usually the best method in this situation.
Condoms, diaphragms, and caps form barriers between the penis and the uterus to prevent sperm from reaching the egg. They may be used with spermicide, a substance that kills sperm. Barrier methods are 92–98 per cent effective, and the male condom is the most effective. Most failures are due to incorrect use.
Before a condom is unrolled on to the penis, the air must be squeezed out of the reservoir (end) so that the condom will not split. After intercourse, the penis must be withdrawn with the condom held on to prevent semen from leaking out.
The closed end of the condom is pushed up to the cervix. The open end extends just beyond the vaginal opening. Make sure that the penis goes inside the condom, not between the condom and the vaginal wall.
Inserting a female condom
The cap is partially filled with spermicide then pushed over thecervix. If intercourse does not occur within 3 hours of inserting it, extra spermicide must be added. To be effective, the cap must be left in place for at least 6 hours after intercourse.
The diaphragm is coated with spermicide on both surfaces. It is positioned so that the concave side covers the cervix. Like the cervical cap, it must be left in place for at least 6 hours after intercourse.
Female hormones that prevent conception may be prescribed as pills, patches, injections, implants, the intrauterine progestogen-only system (IUS), or vaginal rings. Some types of hormonal contraceptive contain only progestogen. This hormone thickens the cervical mucus so that sperm cannot pass through; it also thins the lining of the uterus, which reduces the chance of a fertilized egg implanting successfully. The POP that contains desogestrel also inhibits ovulation. Hormonal contraceptives that contain oestrogen and progestogen work by suppressing ovulation. Hormonal contraceptive methods are over 99 per cent effective, but they must be used exactly as instructed.
The vaginal ring is a flexible plastic ring containing oestrogen and progestogen. It is inserted into the vagina, left in place for 3 weeks, then removed. After a ring-free interval of a week, a new ring is inserted.
Intrauterine progestogen-only system (IUS)
The IUS resembles an IUD, consisting of a T-shaped plastic frame with threads attached to the base. Unlike an IUD, the plastic frame of the IUS is not coated with copper but contains progestogen, which is released slowly and continuously for 5 years. The IUS is positioned in the uterus in the same way as an IUD.
Progestogen-only pill (POP)
The traditional progestogen-only pill must be taken at about the same time each day, for every day of the menstrual cycle. Although the traditional progestogen-only pill is less effective than the combined pill, it does not have the health risks of the combined pill. There is a newer type of progestogen-only pill containing desogestrel that is more effective than the traditional type.
Combined oral contraceptive (COC)
The combined pill contains oestrogen and progestogen. There are various types. With some, you take pills for 21 days and then have 7 pill-free days. With others, you take 21 hormone pills and then 7 inactive pills. You must take the pills in the specified order.
Contraceptive injection and implant
Progestogen is injected into a muscle in your arm or buttock, and it is released into your body over 8–12 weeks. Alternatively, an implant containing progestogen can be inserted under the skin of the upper arm and will remain effective for 3 years.
The contraceptive patch contains oestrogen and progestogen. It is used for 3 weeks out of every 4 of the menstrual cycle, and a new patch is used each week. A patch can be put on any part of the body that is not very hairy and is not sore.
The intrauterine device (IUD) is fitted by a doctor and is left in place for up to 10 years, depending on the type. IUDs are thought to work mainly by stopping sperm from reaching an egg; they may also prevent eggs from implanting in the wall of the uterus. IUDs are over 98 per cent effective.
Intrauterine device (IUD)
An IUD has two threads that extend through the cervix. Once a month, the user should check that the threads are still there in order to make sure that the IUD has not been expelled during menstruation.
Natural methods of contraception are used to identify days in your menstrual cycle when you are fertile and times when you are less likely to conceive. Having identified these times, you can refrain from sex on your fertile days or use another form of contraception. The sympto-thermal method, which is only about 80 per cent effective, is the most commonly used natural method. It is based on two factors: body temperature rising just after ovulation (which occurs 12–16 days before each period) and staying high for at least 3 days; and increased amounts of mucus in the vagina around the time of ovulation. If you plan to use natural methods, seek advice from your doctor first.
Using a temperature chart
You can monitor your fertility by recording your temperature on a chart like the one shown here. Take your temperature at the same time every day, immediately after waking and before getting up. Ovulation (on day 15 on this chart) is followed by a rise in temperature. When you have recorded higher temperatures for 3 days in a row, your fertile time is over. A time of infertility then follows, and this time continues until the last day of your next period.