The beneficial effects of fertility decline on infant mortality were postulated as early as the beginning of the twentieth century by Newsholme and Newman, although at that time, no data were available for the investigation of the authors' hypothesis ( Woodset al. 1988, 1989). In his analysis of the decline in infant mortality in England and Wales, Woods concludes that declining fertility--both marital and illegitimate--since 1870 helped to reduce infant mortality by reducing parity and by increasing spacing between pregnancies.
The impact of fertility decline on infant mortality is of particular interest in the Latin American and Caribbean region. All the family planning programmes that have been developed in the region since the 1960s have as one of their objectives the improvement of maternal and child health ( Taucher 1979a). In terms of maternal health, the principal effect hoped for is a reduction in the frequency of induced abortion, as a result of its replacement by contraception. At the same time it is hoped that the health of both mothers and their children will be favourably affected by the fertility decline resulting from these programmes, through modifications in the distribution of births in terms of the parity and age of the mother and the length of the birth-spacing interval.
In Chile, for example, the principal reason for officially incorporating fertility regulation services into the maternal and child health care programme in 1965 was the high level of maternal morbidity-mortality due to abortion found in that country. In fact, the fertility decline that occurred after 1965 was accompanied by a large drop in the number of hospitalizations related to abortion, and in maternal mortality from this cause ( Taucher 1986).
The literature reviews of Buchanan ( 1976) and Rinehartet al. ( 1985) present numerous examples of the relationship between parity and maternal morbidity-mortality. In the studies that were reviewed, ante-partum and post-partum haemorrhages, hypertension, prolapses, rupture of the uterus, and pregnancy- related toxaemia were some of the complications most often found among high- parity women. On the other hand, some complications occur most commonly among first-time mothers, especially the very young. Matemal mortality increases steadily with parity. Nevertheless, in some studies it has been observed that mortality at the birth of the first child is higher than in the case of the second