Population policy options in the developing world.

The population of the developing world is currently expanding at the unprecedented rate of more than 800 million per decade, and despite anticipated reductions in growth during the 21st century, its size is expected to increase from 4.3 billion today to 10.2 billion in 2100. Past efforts to curb this growth have almost exclusively focused on the implementation of family planning programs to provide contraceptive information, services, and supplies. These programs have been partially successful in reducing birth rates. Further investments in them will have an additional but limited impact on population growth; therefore, other policy options, in particular measures to reduce high demand for births and limit population momentum, are needed.

Does malnutrition affect fecundity? A summary of evidence.

Moderate chronic malnutrition has only a minor effect on fecundity (reproductive capacity), and the resulting effect on fertility (actural reproduction) is very small. Among the fecundity components examined here in noncontracepting populations, age at menarche and the duration of lactational amenorrhea appear to be the ones most affected by malnutrition. But from neither of those effects can a difference in fertility of more than a few percent be expected between poorly and well-nourished women in developing countries.

Fertility policy in China: future options.

A wide range of social, economic, and demographic criteria are used to evaluate China's present one-child policy and five alternative fertility policies that might guide China's population control efforts until the end of the century when the one-child policy is scheduled to be abandoned. These criteria include the policies' macrodemographic impact on total population size and population aging; their microdemographic effects on the family's ability to support the elderly, its economic capabilities, and the position of women; and their cultural acceptability to the majority Han Chinese population. The results suggest that the least desirable strategy is to retain the present policy; all the two-child alternatives perform better than the current one-child policy in achieving the policy goals considered.

The relationship between male circumcision and HIV infection in African populations.

The relationship between HIV seroprevalence and the proportion of uncircumcised males in African countries is examined to determine whether circumcision practices play a role in explaining the large existing variation in the sizes of African HIV epidemics. A review of the anthropological literature yielded estimates of circumcision practices for 409 African ethnic groups from which corresponding national estimates were derived. HIV seroprevalence rates in the capital cities were used as indicators of the relative level of HIV infection of countries. The correlation between these two variables in 37 African countries was high (R = 0.9; P less than 0.001). This finding is consistent with existing clinic-based studies that indicate a lower risk of HIV infection among circumcised males.

PIP: Wide variations in the HIV epidemic exist among the different countries in Africa. The relationship between HIV seroprevalence and the proportion of uncircumcised males is examined to determine whether circumcision practices play a role in explaining the variation in the sizes of the African HIV epidemics. Circumcision practices for 409 African ethnic groups were corresponded with national estimates of HIV infection levels. Although age at circumcision and other ethnic group identity characteristics were known, this information was not considered in this study. HIV seroprevalence rates in the capital cities were used to indicate the relative level of HIV infection in the countries. In 5 countries where more than 3 quarters of males were estimated to be uncircumcised, the average HIV prevalence was 16.4%. In none of the capital cities of these 5 countries was the seroprevalence less than 9.5%. Among the 20 countries where more than 90% of males were circumcised, the average seroprevalence was 0.9% and in no case did it exceed 4%. The correlation between these 2 variables was high (R=0.9%;P 0.001). Although strong population level correlation between circumcision and HIV seroprevalence exists, it does not prove a cause and effect relationship. However, the results are consistent with existing clinic-based studies that indicate a lower risk of HIV infection among circumcised males and suggest that male circumcision is a cofactor in HIV infection.

Intermediate fertility variables and marital fertility rates.

Summary Using relatively simple mathematical techniques, an analysis is made of a comprehensive reproductive model that describes the relationships between a set of intermediate fertility variables and the marital fertility rate. Two types of intermediate fertility variables are distinguished: (1) biological parameters and (2) control variables. A homogeneous model is outlined first. Next, this version is extended to include heterogeneity with respect to fecundability and coital rates. Tests of the model with data from two historical populations (i.e. Crulai, 1674-1742, and Tourouvre au Perche, 1665-1765) demonstrate that the model is, indeed, consistent with observed reproductive behaviour in actual populations.

A dynamic model of the reproductive process.

Summary A dynamic deterministic model of the reproductive process is presented. The model describes and analyses the effect of intermediate fertility variables on fertility. The intermediate fertility variables which are the inputs to the model, include the duration of post-partum amenorrhea, fecundability, incidence of spontaneous and induced abortion, contraceptive use and effectiveness, the distribution of age at first marriage and the age specific risks of marital disruption and remarriage. To test the validity of this model, it is fitted to data obtained from reproductive histories of 512 marriages occurring during the first half of the eighteenth century in Canada.

Contraceptive use and annual acceptors required for fertility transition: results of a projection model.

Major fertility declines in developing countries are invariably accompanied by large increases in contraceptive prevalence and in the annual number of new acceptors. This article applies a target-setting model to make hypothetical projections of trends in prevalence and number of acceptors over the course of a full fertility transition. The sensitivity of these trends to variations in proximate determinants such as the marriage pattern and the duration of lactational amenorrhea, as well as in the discontinuation rate and the method mix, are examined. It is concluded that a contraceptive prevalence of around 75 percent is needed to achieve replacement-level fertility and that variations in proximate determinants other than contraceptive prevalence have only a modest effect on this result. On the other hand, trends in new acceptors are demonstrated to be very sensitive to discontinuation rate changes. As a consequence, it is generally difficult to draw conclusions about trends in fertility from trends in acceptors.

A model of the spread of HIV infection and the demographic impact of AIDS.

The objective of the computer simulation model described here is to project, for periods up to one or more decades, the annual incidence and prevalence of HIV infection and AIDS in a population with given epidemiological, behavioural and demorgraphic characteristics. In addition, the epidemic's impact on a range of demographic variables is calculated. The epidemiological components of the model use a compartmental approach and they are described with sets of linear differential equations. The demographic framework in which the epidemiological components are integrated, is based on a standard cohort component method of population projection. The simulated population is stratified by age, gender, sexual behaviour, marital status and infection/disease status. The concluding section provides an illustrative application of the model to a Central African population. In this hypothetical simulation covering the period from 1975 to 2000, HIV prevalence in the adult population rises from 0 to 21 per cent. By the end of the projection period mortality is about double the level that would have prevailed in the absence of the epidemic, but, owing to the very high birth rates that prevail in most of Africa, the growth rate of the population remains substantially positive.

Trends in unwanted childbearing in the developing world.

This study analyzes trends in unwanted fertility in 20 developing countries, based on data from the World Fertility Surveys and the Demographic and Health Surveys. Although wanted childbearing almost invariably declines as countries move through the fertility transition, the trend in unwanted fertility was found to have an inverted U shape. During the first half of the transition, unwanted fertility tends to rise, and it does not decline until near the end of the transition. This pattern is attributed to the combined effects of an increase in the duration of exposure to the risk of unwanted pregnancy and a rise in contraceptive use as desired family size declines. The substantial variation in unwanted fertility among countries at the same transition stage is caused by variation in the degree of implementation of preferences, the effectiveness of contraceptive use, the rate of induced abortion, and other proximate determinants, such as age at marriage, duration of breastfeeding, and frequency of sexual relations. The principal policy implication from this analysis is that vigorous efforts to reduce unwanted pregnancies through family planning programs and other measures are needed early in the fertility transition because, in their absence, unwanted fertility and abortion rates are likely to rise to high levels.

A method for the estimation of fecundability.

A new method for the estimation of the mean and variance of fecundability is described. The data input required for this procedure is the distribution of the interval from marriage to first birth, or from the resumption of the conception risk after contraction to the subsequent birth. The estimates of the mean and variance of fecundability are obtained by fitting a model to the observed interval distribution. To test the method, it is applied to data from five historical populations. The fecundability means in these populations ranged from 0.18 to 0.31 while the co-efficients of variation all had values near 0.56. A short method for the estimation of the mean of fecundability based on the same model, but not requiring a computer, is also presented.

Infertility and age: not so unresolved: a reply.

PIP: Discusses the issue of whether women who postpone having their 1st child beyond age 30 face a serious risk of involuntary childlessness. A recent study by the Federation CECOS on French women assert that this is the case. This conclusion, in turn, has been criticized in a recent paper by the author, on the basis of results of a study undertaken by Martin Vessey. After critical examination of both studies, the author concludes that women who postpone having their 1st child until their 30s do face an increased risk that they will not be able to conceive. The CECOS study does overstate the case, however, and must be accepted only with reservations. On the other hand, the author's study does understate the increased risk of postponing childbearing, describing it as "modest". Neither of these studies provides information on the decline in fecundity with age among childless women in the U.S., and drawing any conclusions from this data might be misleading for American women.^ieng

The fertility-inhibiting effects of the intermediate fertility variables.

Based on the application of an aggregate reproductive model, this study demonstrates that a small number of intermediate fertility variables are responsible for most of the variation in fertility levels of populations. Four variables--proportion married, contraception, induced abortion, and postpartum infecundability--are generally the most important determinants of fertility; the other intermediate factors are of less interest except in unusual circumstances. These four factors explain 96 percent of the variance in the total fertility rate in a sample of 41 populations that include developing and developed countries as well as historical populations. In the last section, the average fertility effect of the principal intermediate fertility variables is estimated for groups of contemporary populations with different total fertility rates.

PIP: This paper demonstrates that differences in the fertility levels of populations are largely determined by variations in only 4 intermediate variables: proportion married, contraception, induced abortion, and postpartum infecundability. To determine the predictrive value of these 4 variables, the observed total fertility rates of 41 populations that included developed and developing countries as well as historical populations were compared with the model estimates of total fertility rates. Good agreement was found between these 2 fertility levels. The 4 intermediate fertility variables explained 96% of the variation in the observed fertility rate, confirming the general validity of the model. In addition, estimates of the fertility effects of these factors and of the levels of general fertility, marital fertility, and natural fertility were made for contemporary populations at various stages in the fertility transition. The data indicate that the transition from natural to controlled fertility is accompanied by a shortening of postpartum infecundability, a large increase in contraceptive use, and a decline in the proportion married.

Infertility after age 30: a false alarm.

PIP: The author comments on a French study of artificially inseminated French women which reported high levels of infertility and sharp reductions in fertility in women past 30. The implications widely drawn from this study--that women should wait to complete their educations and establish themselves in careers until after they have children--are viewed as invalid, and the findings themselves as highly exaggerated. The levels of infertility experienced by women undergoing artificial insemination are much higher than those experienced by women who are inseminated naturally. The 1 year limit used in the French study to define infertility does not allow sufficient time to determine whether a woman is actually infertile (although the 12 month rates are higher than those found in a survey of US women of reproductive age). In addition, the levels of infertility in the French study are much higher than those found in a carefully controlled study of British women, and higher than rates shown in various historical fertility studies. For reasons which are not as clear, the trends reported in the French study are also much sharper for women aged 30-35 than are those found in studies of women who have not been inseminated artificially. The author concludes that for most women who want to postpone childbearing until their 30s, the risks of becoming infertile may be quite small compared to the benefits that postponement may provide.^ieng

Involuntary childlessness with increasing age.

PIP: As more and more women are postponing childbearing until they are over age 30, much interest and concern has been generated by a recent French study of artificially inseminated women conducted by the Federation CECOS. The study suggests that the risk of being infertile at any age is far from small and that the risk increases sharply not only after age 40, but starting as early as 30. The carefully designed CECOS study provides unique data on conception rates following artificial insemination, but it gives a poor basis for estimating levels and trends in infertility for the general population. Artificial insemination with frozen sperm is considerably less effective in achieving conception than natural insemination. With artificial insemination in presumable fecund women, the CECOS study obtained an average of about 0.1 conceptions/woman/month. In contrast, a comparable rate with natural insemination is typically twice as high, and if the frequency of intercourse is increased, rates over 0.4/month can be expected. The principal cause of the lower conception rate with artificial insemination is the damage done to sperm during the freezing process. Freezing causes a large reduction in motility, and it results in structural and biochemical changes in sperm. CECOS researchers note that a major problem with the freezing of semen is the "incontestable drop in fertilizing capacity." Reliable estimates of age specific levels of permanent (involuntary) infertility have not yet been published for any modern contemporary population. Measures of permanent infertility are available for a number of noncontracepting historical populations. A review of this evidence provided the following average levels of infertility: 4.1% between age 20-24; 5.5% between 25-29; 9.4% between 30-34; and 19.7% between 35-39. These percentages may be excessive at this time to the extent that modern medical technology can eliminate some previously untreatable causes of infertility. The CECOS study also reports that the proportion failing to conceive in 12 cycles rose by 13 percentage points -- from 26-39% -- between the late 20s and the early 30s. This finding would have been important if it applied to the general population, but this increase was only about 4%. Although the rise in infertility with increasing age is not negligible, it is sufficiently modest that many women may decide that the benefits of postponing childbearing in order to establish a career outweight the risks of remaining childless.^ieng