As you can see from the process of sexual reproduction, there are several ways to prevent the sperm and egg from coming together. These methods of contraception fall into the following categories:
- Not engaging in sexual activity - abstinence .
- Preventing a follicle from developing - birth control pills containing synthetic oestrogen and progesterone.
- Placing a barrier between sperm and egg - condoms (male/female), cervical caps, diaphragms.
- Killing the sperm - spermicides.
- Preventing successful implantation - IUDs (coils)
- Surgery - blocking the sperm or egg with surgical procedures like tubal ligations (in women) or vasectomies (in men).
- Timing - avoiding intercourse during the period of maximum fertility - the rhythm method.
The female contraceptive is one of the most popular methods of contraception. This is largely because it does not interfere with sexual intercourse. There are two types of pill. The combined pill which contains oestrogen and progesterone is the one that is examined in detail in this section. The other pill is called the mini-pill and contains progesterone only.
The combined pill works by maintaining the concentrations of oestrogen and progesterone at their pre-ovulatory concentrations. At these concentrations these hormones have a negative feedback effect on the production on FSH and LH so the surge of LH and FSH is prevented so ovulation does not take place.