from extreme ages to central ages, which corresponds to fewer possible risks to mother and child.
Table 1.8 also shows the proportion of births by different age-groups of women, with the Latin American countries grouped according to their present fertility levels. For this purpose the ages have been classified into three groups: the youngest, aged 15 to 19, or adolescent fertility; women aged 20 to 34 years, which make up the central fertility ages; and those aged 35 and over, or of advanced age for fertility. The first and last groups are those at high risk of morbidity and mortality both for the mother and for the child, and for this reason their behaviour is observed separately.
As expected, the greatest contribution to total fertility in all cases comes from the central ages, between 20 and 34 years. Fertility ranged from between 66 and 76 per cent in 1950-5 to between 69 and 78 per cent in 1985-90, showing that generally there is a greater concentration of fertility in this age-group through time and declines in fertility. The exceptions are Argentina, Uruguay, Cuba, and El Salvador, where, in contrast, a reduction in the percentage of births to women of central ages is observed.
Despite this greater concentration of fertility in central ages, a relatively high proportion of births is attributed to the groups of women who have been classified as having high birth risk, those below age 20 and over age 34. The proportion of all births contributed by these women, which in 1950-5 varied between approximately 25 and 35 per cent, has declined but is still between 25 and 30 per cent in most countries.
Although this difference is not very striking, the higher the level of fertility, the higher the contribution made to total fertility or to total births by the women at the extremes of the range of reproductive ages. Procreation begins very early and lasts beyond first youth, which leads to the formation of larger families. The changes in social and economic factors which favour the decline of fertility affect the younger women since they postpone childbearing, and the older women because they stop bearing children sooner and may already have the number of children they wish.
The high-risk group of women is made up of two very different subgroups. When comparing each of the selected time periods, the contribution of women aged 35 and over was higher than that of the younger group in the majority of cases in 1950-5. The contrary is observed in 1985-90, since the relative contribution of women aged 35 and over to total fertility has diminished considerably with the decline in fertility, independently of the present fertility rate in each country.
The 1950s were characterized by high fertility rates in most Latin American countries. The TFR reached an average of 6 children per woman. Following a