Human contraception: development of new scientific opportunities

Our current methods of contraception were largely developed in the 1950s and 1960s. Collectively these methods can limit population growth, although their acceptability at a personal level remains marginal. The number of abortions in the UK has risen progressively, from < 130,000 in 1980 to > 170,000 in 1990, and more people have sought sterilization. In global terms, population continues to increase on a scale unrecorded in human history. More than 800 million people, equal to the current population of North America, Europe and Japan, will be added to the world population of 5400 million by the year 2000, with 95% of the increase located in the economically and environmentally fragile regions of the South. Worldwide, in these 8 years, about 500 million abortions will be performed (> 40% by unsafe methods), about 80 million children under 1 year of age will die, and about 5 million women with be lost from pregnancy-related causes. Over 100 million people, most in Africa, Latin America, India and South-east Asia, will have become infected with human immunodeficiency virus. Religious, commercial and political pressures continue to constrain the development and distribution of contraceptive products, though some changes are in sight. Contraception is now being advanced in the broader context of neonatal and maternal health care. New scientific opportunities are also evident, with the potential to advance contraception in a quantal step. Third generation contraceptive steroids, anti-steroids, steroid-releasing vaginal rings, and injectable steroid preparations for men are all under clinical trial. Developments in the longer term, however, could hinge upon the greater specificity afforded by the manipulation of regulatory peptides. Agonists, antagonists and binding proteins for GnRH and the gonadotrophins are being investigated in an attempt to regulate the pituitary-gonadal axis more precisely. Inhibition of this axis may require the provision of low level steroid replacement, appropriately titrated to provide positive health care in the context of menstrual cyclicity, well-being, breast cancer and osteoporosis. Attempts are being made to identify and intercept the highly specific signals involved in fertilization and the maternal recognition of pregnancy, with the current clinical focus on the immunoneutralization of beta human chorionic gonadotrophin (beta hCG). More specific and more acceptable targets might include peptides involved in sperm-zona adhesion and sperm activation, sperm-oocyte fusion, and sperm-activated oocyte cleavage. The interception of these signals would prevent fertilization, implantation or both, and yet leave the hormonal profile of the menstrual cycle unchanged.(ABSTRACT TRUNCATED AT 400 WORDS)