Contraception has come a long way since man first fumbled by candlelight with a combination of animal bladders, various lengths of intestine, and a great deal of luck. These early cumbersome devices may have scored low in protection and hygiene, not to mention sensitivity, but they did for the first time allow couples to prevent at least some unwanted pregnancies.
Since those days, the protection rates of contraceptives have been rising and are now at the stage that, on the pill, only one in 1,000 women who use it properly for a year are likely to become pregnant.
It is 40 years since the advent of the pill revolutionised contraception. It has since been taken by 200 million women worldwide. Despite numerous health scares, and following some refining of its formula, the pill is probably as near as we will get to the perfect contraceptive. The pill, the condom and vasectomies are now the most popular forms of contraception.
But while the protection rates they provide are good when they are used perfectly, most contraceptives are not used perfectly. New research from America shows that although the condom may be 97 per cent effective if used perfectly, in reality 14 women in every 100 are likely to become pregnant after a year. Forgetting to take the pill also decreases the protective rate by a factor of 30.
Because of this gap between perfect and typical use, and the need to attract more people to using contraceptives, the race is now on to develop a new generation of devices. In 40 years' time, the contraceptives we use may have undergone another revolution.
Once-a-month female pills, transdermal patches, pills that eliminate periods, vaginal hormonal rings, contraceptive creams that stop the spread of sexual diseases, male hormone pills, sperm-killing antibody pills, and even superglue vasectomies, are at various stages of development.
"We have to make sure that we provide a wide range. The problem with contraceptive uptake is related to the choice of contraceptives you provide. If people can choose something that suits them at that particular time in their life, they are more likely to use it,'' says Professor David Baird at the centre for Reproductive Biology, at Edinburgh University.
"Demographic forces, prevalence of disease, and social and cultural factors influence not only the use of contraceptives, but also the development of new methods. People are becoming sexually active younger, and bearing children later, or in many developed countries forgoing it altogether. The public also wants more natural products which are perceived to be safer, but at the same time demands that contraceptives are also perfectly effective.''
The first new developments expected within the next five years will be delivery systems for existing methods of contraception. Transdermal patches delivering pill-like hormone combinations, and similar to those used in HRT, are expected to be licensed soon, as well as vaginal rings which also secrete hormones.
Each has advantages over the existing oral pill. Both mean that the hormones go directly into the blood without having to be metabolised by the body, and so lower amounts of hormones are needed. In addition, the levels of hormones is more uniform, and does not have the peaks and troughs associated with the oral pill.
Professor Baird, who is co-author of a report on the future of contraception published in the Western Journal of Medicine, predicts that the first major development will be the anti-progestogen pills. "These will be much better for some women because they will aim to stop ovulation. That is important because there is no health benefit to a period, but there is a lot of morbidity associated with it. A lot of a gynaecologist's practice is taken up with period-related problems.
"When we have done surveys asking women if they would use such a contraceptive and 20 per cent of 20-year-olds said they would, and 60 per cent of 40-year-olds. It will be a major advantage to women and, technically, it could be on the market within five years. That, I think, is probably going to be the biggest development in the short term.''
The long-awaited male pill could also be here in five to 10 years. One of the big problems in developing this pill has been the sheer scale of the problem. While a woman usually releases only one egg per ovulation cycle, the average man generates about 1,000 or so sperm every minute.
Male pill researchers aim to put male hormones into the blood stream directly so that the body turns off production of sperm. This idea is based on the theory that the circulating androgens will instruct the brain to slow down the production of gonadotrophin-releasing and other hormones.
In 10 years' time contraceptive immunisation may become available, based on the concept that sperm is an alien material to the female body. Other foreign invaders, like bugs and viruses, are attacked by the cells of the immune system, but sperm has a permanent pass to get through. The idea behind immunisation is that the immune system can be taught to recognise sperm as an invader and kill it. Female vaccines could also stimulate the production of antibodies that would bind to the surface of the ovulated egg and form a shield that could not be penetrated by sperm.
Also in the pipeline are anti viral creams to protect against sexually transmitted diseases: "Heterosexual intercourse is now the main route of transmissions of the HIV. Although condoms reduce the risk of infection, there is a pressing need for new methods of protection in the shape of anti viral and spermicidal agents,'' says Professor Baird.
While scientists are forging ahead with new types of contraceptives that will emerge over the next five to 20 years, others are refining and improving existing methods to make them more patient-friendly and more effective. Superglue, for example, may seem an unlikely male contraceptive, but it is being tried in a new type of vasectomy.
Doctors have been using the glue as a kind of chemical vasectomy to stop the progress of fertile sperm. Conventional vasectomy is more sterilisation than contraception, and the big advantage of the glue-based technique is that it would be easily reversible and could be used as a temporary contraceptive technique.
In a traditional vasectomy, which has now been carried out on around 50 million men - mainly in Europe and America, the tube along which sperm must travel from the epididymis to the urethra is effectively blocked.
It's been known for some time that apart from abstinence, a vasectomy is just about the best form of male contraception for those couples who do not want any more children. But although it is highly effective, it is not used as a temporary form of contraception, largely because surgery to reverse a vasectomy fertility is expensive and doesn't always work.
But the new glue-based method now being tried may make the reversible vasectomy possible. In this approach n-butyl cyanoacrylate, the compound that makes Krazy Glue, is used to block the tube and stop the sperm travelling through. Researchers say that when a couple want to start having a family, the glue plug in the vas deferens [the duct which conveys sperm from the testicle to the urethra] is simply dissolved with the injection of another chemical.
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