The purpose of contraception is to avoid conceiving during sexual activity. This can be achieved in a number of ways. There are certain health conditions, pregnancy history and age of the couple that may preclude particular contraceptive methods. There are a wide range of contraceptive options and the following information provides a brief summary. Ken can help you with your decision making.


Pearl Index

The Pearl Index of a contraceptive technique refers to its effectiveness. It is calculated as the number of women who will become pregnant per 100 women per year having regular sexual activity. Without any contraception, 50-80% will conceive. The lower the Pearl Index the greater degree of contraception is being achieved. A Pearl Index of 2 means that for a 100 couples who have regular intercourse using a particular form of contraception for one year, two couples will become pregnant during that time.


Withdrawal/Coitus Interruptus

This is a surprisingly frequently used form of contraception in many age groups. It has the benefits of being simple and cheap, but the disadvantage of potentially reduced sexual enjoyment through fear of unintended pregnancy. Timing is critical and unfortunately there are some sperm that are released from the penis prior to ejaculation and this may contribute factor to its failure rate.

Billing’s Method

This method relies upon the observation of the cervical mucous. Around the time of ovulation there is increased mucous production which is clear and slippery. This occurs about 14 days prior to the next menstrual period (not necessarily 14 days after the previous menstrual period as the first part of the menstrual cycle can vary in its length). During this time of likely ovulation, intercourse can either be avoided or alternative measures such as barrier methods or withdrawal used. This technique is particularly useful for couples where the women has a regular menstrual cycle and is also able to observe these changes in her cervical mucous.


Pearl Index: 5-15

These are a readily available form of contraception which have the added benefit of a degree of protection against sexually transmitted infections. It is important that condoms are used properly. They can deteriorate if stored in a hot environment, or may rupture during sexual activity, or slip off after ejaculation when the penis is no longer erect.


Pearl Index: 5-15

The contraceptive diaphragm is now used infrequently. They have the advantage of being able to be inserted well before sexual intercourse takes place. The obvious disadvantage is when sexual intercourse has not been foreseen and the diaphragm not close at hand. Diaphragms need to be sized by a health care professional such as a General Practitioner, Gynaecologist or a Family Planning Clinic.


Emergency Contraception (the ‘morning-after pill’)

Postinor‐2 is a progesterone‐based tablet for use in an emergency where there has been unprotected intercourse. It is most effective if taken as soon as possible after intercourse, but still may be effective up to 72 hours afterwards. It does not require a prescription and can be obtained from most pharmacists. This is not suitable for routine contraception because of its potential for failure and because it can cause menstrual irregularities.

Combined Oral Contraceptive Pill

Pearl Index: 0.8

The combined oral contraceptive pill, containing both oestrogen and progesterone, has been available for over 50 years. The oestrogen component is responsible for inhibiting ovulation. The progesterone prevents the lining of the womb (endometrium) from becoming too thick. Benefits of ‘the pill’ include reduced menstrual bleeding in a predictable fashion and reduced period pain. It is important to take the pill as directed as its contraceptive effectiveness is reduced by missing pills, malabsorption of the pill because of vomiting or diarrhoea, the use of some antibiotics, or medications (e.g. anti‐convulsant drugs) that effect the metabolism of the pill by the liver. The pill is comparatively safe, but there are some women for whom its use may be dangerous, such as those with a past history of deep vein thrombosis/pulmonary embolism, recent breast cancer, high blood pressure and heart disease.

There are two main types of combined oral contraceptive pill; monophasic (a pill which has the same strength and proportion of hormone in every single tablet) and triphasic (one that has three different strengths of hormones throughout the cycle).

One advantage of a monophasic pill is that it is possible to manipulate the length of your menstrual cycle by staying on the pill for greater than the usual three weeks and thereby postponing a period for events such as exams and holidays (although this doesn’t work for all women). Women who are on a triphasic pill may not be able to manipulate their periods because of the variation in hormone dosage that this entails. The combined oral contraceptive pill cannot be used when breast feeding as the oestrogen usually suppresses milk production.


Pearl Index: 0.8

This is a recently developed form of contraception. A woman places the plastic ring within her vagina where it will stay for 21-24 days. It is impregnated with the same oestrogen and progesterone that are in the combined oral contraceptive pill and will leach out both hormones while it is in the vagina. It is then removed for a full seven days and a new ring then inserted. The benefits of this method are a lower hormonal dose and it is easier than remembering to take the pill. These devices generally do not fall out nor cause infection, but a number of women feel awkward about having this device inside their vagina although it does not interfere with sexual intercourse.

Progesterone‐Only Pill (the ‘minipill’)

Pearl Index: 4-5

The progesterone‐only pill is typically used for breastfeeding mothers, but also for women who have a history of thrombosis, high blood pressure or cardiac disease, for whom an oestrogen‐containing pill may not be suitable. It is believed that its contraceptive action is due to thickening of the cervical mucous preventing penetration of sperm into the uterine cavity. This pill is taken every single day regardless of menstrual bleeding and timing is critical. The progesterone‐only pill needs approximately 3 hours to be effective and wears off 3 hours prior to the next day's tablet. It therefore needs to be taken at the same time every single day and also intercourse avoided both 3 hours before and 3 hours after taking this pill.


Pearl Index: 0.2

This is a highly effective and also quickly reversible contraceptive option. This plastic rod is the size of a matchstick and is inserted in the upper arm under local anaesthetic either by your General Practitioner or Gynaecologist. It is effective for three years but a major reason for discontinuation is troublesome and prolonged menstrual bleeding. Some women may also develop fluid retention, weight gain and headaches. In women who do not suffer these side effects it is a very reliable form of contraception. It is particularly useful for women who are forgetful in taking the contraceptive pill.

Mirena Intrauterine System

Pearl Index: 0.3

Although early intrauterine devices were associated with heavy painful periods, recent intrauterine devices have revolutionised both contraception and management of heavy periods. Intrauterine devices keep working for a long time, and once inserted requires very little attention.

The Mirena intrauterine device is impregnated with a progesterone hormone called Levonorgestrel which has two main actions. Firstly, it causes a thickening of cervical mucous making it impenetrable to sperm so that only 1:300 couples will conceive per year with this device. Secondly, it causes thinning of the endometrium (lining of the womb) which results in very light menstrual bleeding.

After insertion of the Mirena device, the progressive thinning of the endometrium results in a persistent brown discharge. This usually ends within three months. After three months the volume of menstrual blood lost with each period is equivalent to 15% of what it had previously been. By 12 months this volume of menstrual blood is reduced to just 3%. It is not uncommon for women to report having very little in the way of any period at all for several years with the Mirena device in place. This is not unhealthy. Normal menstrual bleeding is due to the shedding of endometrium that has become thick during a normal menstrual cycle. This thickening occurs in preparation for the reception of a fertilised egg and if pregnancy does not occur in that particular cycle then the endometrium is shed together with loss of some blood. In the situation of a Mirena device being present the endometrium is so thin that there is simply very little to shed. This absence of menstrual bleeding may concern a few women as a sign of undiagnosed pregnancy, but in the unlikely event of pregnancy with a Mirena device the woman will usually experience other symptoms such as breast tenderness, nausea, change in taste for common things such as coffee and toothpaste. If any of these symptoms were to occur then it would be advisable to do a home pregnancy test.

The Mirena device is inserted through the cervix, into the uterine cavity. The technique of insertion is relatively straightforward. The optimal time for insertion is within the first three days of a menstrual period. At this time the cervix is softer and slightly dilated as compared to other times in the menstrual cycle. In women who have never been pregnant and those that have not experienced labour, the cervix can be quite tight and the insertion too painful to conduct as an outpatient. In such circumstances the Mirena can be inserted under general anaesthesia in hospital.

A small number of women (1%), experience expulsion of the Mirena device. Therefore, regular checking for the presence of the Mirena string on a monthly basis is advised. This is done by inserting a finger into the vagina to detect the cervix (which has the same consistency as the end of your nose) and feeling for the string. It is important that the string is not pulled on as this may dislodge the device. If the string can’t be felt then you should visit your General Practitioner or myself as soon as possible for a simple speculum examination to see if the string is present. There are times when the string may curl up on itself and retract within the uterine cavity. A pelvic ultrasound is then needed to confirm that the Mirena is still in place.

The risk of infection with the Mirena device is very low. Infection can occur in the first 20 days after insertion. The Mirena should be used with caution in women who are in a casual sexual relationship as they are at higher risk of sexually transmitted infections, which can be aggravated by the presence of the Mirena device, the risk being lessened by also using condoms. In the unlikely event of pregnancy occurring it is important that the Mirena device be removed as soon as possible because of the risk of septic miscarriage.

The Mirena device does not interfere with sexual activity in any way. The performance of pap smears is unchanged. If the Mirena device proves to be unsuitable for you then its removal is usually very straightforward and painless as an outpatient.