For most of man's existence, natural checks on fertility ensured that the n
umbers of the population more or less matched the resources available. It i
s only in the last few generations that man has so dominated the natural en
vironment that the numbers of people in the world have increased exponentia
lly, unchecked by natural disasters such as disease and starvation. Coincid
ental with extended life expectancy, the fertility rate of individual women
has increased with the advent of bottle feeding and the decline in the con
traceptive effects of breast feeding. Contraception has become increasingly
important to individuals, allowing them to break free from the 'burden of
excessive fertility'(1).