Fertility concerns the addition of new members to a population by birth; that is, the actual performance of a population in bearing children. It is one of the components of population change. Births and deaths are technically referred to as fertility and mortality in demography. It differs from fecundity, which refers to the physiological capability of women to reproduce. Fertility is directly determined by a number of factors that in turn, are affected by a great many social, cultural, economic, health and other environmental factors.
Populations which do not take up explicit measures to limit the number of births are said to experience NATURAL FERTILITY. In such populations, fertility is considered to be an essentially biological phenomenon and its level varies mainly due to social customs such as varying age at marriages and differencing breastfeeding and weaning practices and not due to any contraceptive measures adopted for spacing of children.
Some women are, for various reasons, unable to bear any children. Such women are said to be STERILE or infertile. Sterility is of two types; one is PRIMARY STERILITY and other is SECONDARY STERILITY. Primary sterility refers to women who have not produced any live births at all. Secondary sterility refers to the women who have become sterile after the birth of one or more children.
‘Even though childbearing is basically a biological phenomenon, it is generally argued that variations in the level of fertility are not primarily due to the differences in physiological capacity but more often produced by responses of individuals and couples to the social systems in which they live. Biological and behavioural factors which directly influence fertility and through which social, economic and other factors come to influence childbearing are called PROXIMATE DETERMINANTS of fertility. Scholars have all along differed and still differ on the importance of different factors that contribute to a given level of fertility in a population and of the contributions of family planning programs towards reduction of fertility levels in a population. No single theoretical model has yet been developed which captures all aspects of fertility behaviour. Empirical work conducted in developing countries has suggested that the key variables that contribute to variations in fertility behaviour at the aggregate or individual level are: education and labour force participation of women, marital patterns (age at marriage), the duration of breast feeding, child mortality levels and contraceptive use. The transition in the fertility patterns of countries from high to low levels of fertility has accompanied their levels of industrialisation and development. Fertility is considered to be closely linked with socio-economic development and process of industrialisation. In their theories of fertility, since the early 1950s, economists, utilising various concepts of economics, viewed fertility performance simply as ‘economic behaviour’, a rational ‘economic response’ and the sociological significance of reproduction was not included in the economic analysis of fertility’ (Srinivasan 1998).
‘There is always a big difference between the actual fertility and the maximum number of children that is physiologically possible for a woman to bear. Theoretically, if a woman gave birth to one child every 10 months over a period of 31 years (14 to 45), she could produce 37 children during the physiologically limited childbearing period. Even, if she gave birth to a child every 15 months throughout her reproductive period, she would produce a total of 25 children. Of course, no population reaches that maximum and there is great variability between the reproductive productivity of women. According to ‘The Guinness Book of World Records’ , the largest number of children given birth by a woman and officially recorded is 69 by a woman who lived near Moscow during 18th century (16 pairs of twins, seven sets of triplets and four sets of quadruplets). A religious sect living on the borders of the USA and Canada, called ‘Hutterites’, have recorded the highest average for any community which is about 11 births per woman. In this community, culture places a high positive value for couples on having children and any form of birth control is considered to be sinful’(Srinivasan 1998).