Hormones may be used to prevent ovulation and to cause other changes in the reproductive tract that prevent pregnancy. The hormones may be given by mouth, or may be absorbed from slow-release implants under the skin, injections into muscle or from hormone-containing devices such as vaginal rings and IUDs. To most people, hormonal contraception means ‘the Pill’, so I’ll describe it first.
The oral contraceptive pill – usually called the Pill or ОС – has been used for more than 30 years in Australia. More than 70 million women around the world are now using it to plan their families.
Oral contraceptives contain synthetic hormones that are very similar to the hormones produced naturally by the ovaries. There are probably no other drugs on the market that have been more thoroughly tested, both in the laboratory and by the millions of women who have used them.
There are two main types of oral contraceptive. The most commonly used is called the ‘combined Pill’ and contains both ovarian hormones, an oestrogen and a progestogen. The ‘mini-Pill’ contains only a progestogen, and is also known as the ‘progestogen-only-Pill’ or POP.
The combined Pill
This is what is usually meant when people speak of ‘the Pill’. All combined Pills available in Australia contain one of two types of oestrogen (which have very similar effects) plus one of six types of progestogen.
• Monophasic Pills have the same amount of each hormone in every tablet that is taken throughout the Pill cycle.
• Biphasic Pills have a reduced amount of progestogen in the tablets that are taken for the first half of the cycle.
• Triphasic Pills containing three different combinations of the hormones are taken in three consecutive phases over the cycle.
When oral contraceptives were first introduced, they contained much higher doses of hormones than today’s Pills. All the Pills on the market now are low-dose compared with the early Pills. Some contain less hormones than others. Reducing the dose has reduced or eliminated many of the side-effects of Pills with higher doses.