The average number of births to a cohort of women up to the end of the reproductive age period (estimated on the basis of the age-specific rates observed during a given period) is called :

Total Fertility Rate

The correct answer is Option (3) - Total Fertility Rate.

The total fertility rate refers to the total number of live births that a hypothetical woman would have if she lived through the reproductive age group and had the average number of babies in each segment of this age group as determined by the age-specific fertility rates for that area. Another way of expressing this is that the total fertility rate is the ‘the average number of births to a cohort of women up to the end of the reproductive age period (estimated on the basis of the age-specific rates observed during a given period)’