Abstract

Fertility may be defined as the reproductive performance measured by actual number of births of an individual a couple or a group of population. Fertility must not be confused with fecundity which may normally be defined as the physiological capacity of a men women or couple, to reproduce live births. Fertility is statistical concept with social relevance, whereas fecundity is a logical concept.      

             Fertility indicates the actual level of reproductive performance determined by social, cultural, Psychological as well as economic factors. These terms are used quite loosely in medical literature end are sometimes treated as being synonymous (United Nations,1958, p-38).

             Fertility measures the rate at which a population adds to itself by births. These measurements may be related to something for example, the total population of the country / total population of the women in the country / region, total women of the child bearing age, total married women etc. If fertility is measured with respect to married couple, we will be ignoring births given by unmarried mothers or widows or births which resulted from pregnancies

          The crude birth rate provides a first approximation in any study of fertility and has the advantage of bringing out exact date at which the population in creases through births but the major drawback, of such an index is that it uses the total population as denominator though the entire population is never involved in the process of reproduction (Clarke, 1981, p-35). However this measure of fertility is very common particularly in developing countries.

            Child woman ration is a useful index of fertility as it takes into account only females in the reproductive age group. However it also suffers from certain drawback. First, it cannot be tabulated for a year other census years because age distribution data are available for census years only second, it includes only the surviving children below five years of age and not all the children who were actually born. Third it takes into account all females in 15-44 years age groups irrespective of their marital status.  

             The general fertility rate is the number of the live births in a year born per mile women of normal reproductive age group. It is a definite improvement over crude birth rate as it takes into account only the female population of reproductive age group but it is not an effective refinement for two reasons. Firstly it is related to all the women in child - bearing age group irrespective of marital status and secondly the Fecundity of women is not same during the entire span of child bearing period. It may be pointed out the child bearing rate is appreciably higher in 20-29 age group than in 15-19 and 30-44 age groups.

              Age specific fertility rate is the average occurrence of live births to the females of a specific age group per mile women in that particular age group. The total fertility rate is another age sex adjusted measure of fertility which has been regarded as the most sensitive and the most meaningful cross-sectional measure of fertility. It may be defined as the average number of children that would be born alive to a woman (or group of woman) during her life time if during her child bearing years she were to bear children at such age in accord with prevailing age specific fertility rate.

             Gross reproduction rate represents the average number of daughters, which ignoring mortality replaces their mothers assuming that the age and sex specific fertility rates for the current period were to continue indefinitely (Woods, 1979, p-96).

              It is therefore a measure if the average number of daughter produced by the woman during her female babies born per mile of female population in reproductive age group.

              Besides these there are some other measures of fertility some of them are, cumulative fertility rate, and net reproduction rate completed fertility rate and cohort fertility.