Introduction (cont.)
In demography fertility is entirely concerned with the number of living babies that women give birth to. This is immediately different from the clinical concept of fertility, which is the potential of a woman to become pregnant and bear a live child. This is often a cause of confusion so let’s make it very clear – fertility in demography is the bearing of live children. A fertile woman is one who has borne live children, even if they have subsequently died.
The reason for this approach is that it is only live births that produce new members of the population. Anything that happens during conception, pregnancy and parturition (birth) does not affect population size until a live baby is delivered.
Miscarriages, abortions and stillbirths are not considered in the formal measures of fertility at all. They may be considered in other medical rates e.g. peri-natal mortality rate, but they do not enter into demographic measures of fertility. They may also be considered in an area of demography called birth–interval analysis and as reasons why fertility is lower than expected but they are not themselves evidence of fertility in the demographic sense.
The term in demography that equates to the clinical concept of fertility – i.e. potential fertility is fecundity and the related term fecundability. In demography a woman is not a fertile woman until she has actually borne a live child. Prior to that she will be considered a fecund woman if she is within a certain age range and there is no physical reason why she should not have children.
Male fertility: It is quite possible to analyse fertility based on fatherhood rather than motherhood. This can be an interesting area of research but it is not commonly done. One problem encountered is that verifying paternity is more problematic than verifying maternity.