On Postponement and Birth Intervals

Abstract

Much of the literature on fertility transition presumes that women birth control is practiced either to limit family size or to space births. This paper argues that women also use contraception to postpone pregnancy. Postponement is not synonymous with spacing. It arises when women delay their next birth for indefinite periods for reasons unrelated to the age of their youngest child, but without deciding not to have any more children. Postponement has a distinctive impact on the shape of birth interval distributions that differs from those of family size limitation, birth spacing, or a mixture of the two behaviours. Some populations, such as that in South Africa, have developed fertility regimes characterized by birth intervals far longer than can be accounted for by birth spacing. Postponement of further childbearing that eventually becomes permanent may be an important driver of the transition to lower fertility in sub-Saharan Africa. Timaeus & Moultrie 3The main immediate motivation for using contraception is obvious: it is to avoid pregnancy, or at least to reduce the risk of conception associated with sexual intercourse. In other words, contraception is used for birth control. The reasons why women and their partners may wish to avoid pregnancy and childbearing are many and varied. However, much of the demographic literature on fertility transition classifies motives for birth control into two mutually exclusive and exhaustive theoretical categories -the limitation of family size and the spacing of births.This paper suggests that a third important motive exists for using contraception. It is to postpone or delay pregnancy and giving birth. Birth postponement is not synonymous with birth spacing. It is conceptually distinct and has a different impact on birth interval distributions. Fertility regimes characterized by very long birth intervals cannot arise from spacing but can only be explained by widespread postponement of births achieved by contraceptive and other means. Postponement can have a substantial impact on aggregate fertility. In particular, it may be an important driver of fertility decline in Africa.The arguments just summarized are developed in successive sections of the paper. The first of these critically reviews the literature on fertility intentions and motivations for contraceptive use. It argues that the substantive, measurement, and programmatic concerns of demography have tended to direct researchers' attention away from careful consideration of reasons for practicing birth control other than family size limitation. While the importance of distinguishing postponement of births from spacing of births has been pointed out before, it has not become part of the commonplace wisdom of everyone studying fertility transition.The second substantive section of the paper considers birth interval distributions. It argues that the impact of contraceptive use on the duration-specific hazard of giving birth differs depending on whether contraception is being used for stopping, spacing, or post...

Modelling period fertility: Schooling and intervals following a birth in Eastern Africa

“…Among the subpopulations where the longest times to next birth have emerged, the changes in duration-specific fertility schedules strongly suggest that postponement was the most common motive for birth control, particularly in Zimbabwe. In this sense, the Modelling fertility in Eastern Africa 13 results of this study largely support Timaeus and Moultrie's (2008) assertion that fertility transition in sub-Saharan Africa is seeing the emergence of very long birth intervals, which cannot readily be accounted for by birth spacing as it is usually envisaged. However, fertility in Eastern Africa is changing in a more complex way than any of the current literature suggests.…”

“…The height of the distribution does not change because women's preferences for a particular family size have not changed, as shown by the dotted line in Figure 1 (Timaeus and Moultrie 2008). Third, the distribution produced in a hypothetical population in which women intend to postpone their next birth for an initially indefinite period shows lower fertility at shorter durations since the previous birth and higher fertility at longer durations than the base distribution (also shown in Figure 1).…”

“…Finally, in the populations examined, the lengthening of times to next birth varied little by age or parity (Moultrie et al 2012). Timaeus and Moultrie (2008) argued that understanding this pattern of fertility change requires scholars of population to re-examine the way we theorize and categorize fertility intentions. They proposed the concept of postponement as a third family building strategy, which is distinct from both family size limitation and birth spacing, that may explain the lengthening of birth intervals in sub-Saharan Africa.…”

Contraceptive use and lengthening birth intervals in rural and urban Eastern Africa

“…We have shown that this trend of lengthening is seen even when only closed birth intervals are included in the analysis. This phenomenon has been observed in a number of other studies, including those of Moultrie and colleagues (Moultrie, Sayi, and Timaeus 2012;Timaeus and Moultrie 2008) and Casterline and colleagues (Bongaarts and Casterline 2012;Casterline and Odden 2016). Despite a recent decrease in the reported length of intervals in Zimbabwe, both conditional and unconditional median birth intervals at the national level are longer in Zimbabwe than in Ethiopia, Kenya, and Tanzania.…”

“…Similarly, Lightbourne (1985) shows that in World Fertility Surveys (WFS), even after birth intervals longer than five years, many women report wanting neither to stop childbearing nor to space a birth, but still report desiring to delay their next conception. We question the traditional demographic presumption that the open birth intervals of limiters are qualitatively different from the closed intervals of non-limiters (Cleland and Rutstein 1986;Timaeus and Moultrie 2008).…”