Motivations for the use of birth control: Evidence from West Africa

A conventional assumption in the family planning literature is that birth control in developing countries is first adopted by high parity women who wish to cease childbearing. The empirical support for this belief has mainly been drawn from interview surveys on the motivations for, and the timing of, the inception of birth control among married women in areas where there is no cultural precedent for birth spacing by traditional means. This study, on the other hand, is based on data drawn from an area sample of 6,606 women, married or single, aged 15–59, in Ibadan, Nigeria, where there is a tradition for the practice of abstinence after a birth for the purpose of birth spacing. The Nigerian pattern revealed in the data presented here is indeed distinctive in many respects: (a) although premarital sex is prevalent, levels of premarital contraception are high; and (b) within marriage, spacing is the most prominent motivation for contraceptive practice, more important than the limitation of family size.     

Individual and aggregate influences on the age at first birth

This study examines the role of both individual adolescent expectations of market and nonmarket income and aggregate influences on first birth timing for Blacks and Whites and for three birth cohorts of American women. Using two panels of the National Longitudinal surveys, results suggest that between-race differences in age at first birth result from differences in individual expectations about market and nonmarket income. Cohort differences in age at first birth result from relationship differences in both individual and aggregate influences, with aggregate influences differentially altering the role of individual expectations on first birth timing. These results suggest that employment policies that reduce poverty and increase wages would effectively delay childbearing. For Blacks, since early childbearing results from lower expectations about future economic success, similar fertility timing patterns between the races would result if Blacks had White employment and wage levels. Over time, these employment and wage policies will not only alter individual expectations about economic success but also will alter the impact of expectations on fertility timing.     

Modelling the Inverse Association between Breastfeeding and Contraceptive Use

Previous studies of the inverse association between breastfeeding and contraceptive use have relied on current status data on at least one of the variables. In this paper we suggest a new way of modelling the joint temporal association of the adoption of contraception and the termination of breastfeeding over the course of a birth interval. The approach is implemented with survey data from rural Mexico. It involves first estimating a competing-risks model in which both hazards are considered simultaneous, together with a set of relevant covariates. Conditional analyses are then carried out to estimate the hazards of each event conditional on the timing of the other. By comparing the covariates, we gauge the extent to which the occurrence of one event raises or lowers the hazard of the other. The results show that, in rural Mexico, the timing of the termination of breastfeeding and that of starting contraceptive use are closely related, and that there exists a surprisingly neat interval of 120 days in which the action takes place.     

White and nonwhite trends in first birth timing: Comparisons using vital registration and current population surveys

The magnitude of racial differences in first birth timing vary greatly depending upon the data sources from which they are estimated. Vital registration data (Heuser 1976; with updates from the National Center for Health Statistics 1974–1990) show that in recent years nonwhites have higher risks of a first birth at virtually all ages compared to whites. As a result very large and historically novel differentials in childlessness are forecast using these data (see Rindfuss et al. 1988; Chen & Morgan 1991; Morgan & Chen 1992). However, retrospective fertility history data collected from the 1980, 1985 and 1990 Current Population Surveys (CPS) suggest much smaller racial differences in completed childlessness and isolate racial differences in probabilities of first births at young ages. Differences also exist between theses two series for whites prior to the mid-1960s but not afterwards. Reasons for these differing estimates are suggested and examined. We conclude that a substantial portion of the differences result from an accumulation of biases in the vital registration estimates that affect primarily estimates of first birth timing. Thus, the CPS data provide a more firm basis for racial comparisons of first birth timing.     

Is the Association Between Education and Fertility Postponement Causal? The Role of Family Background Factors

A large body of literature has demonstrated a positive relationship between education and age at first birth. However, this relationship may be partly spurious because of family background factors that cannot be controlled for in most research designs. We investigate the extent to which education is causally related to later age at first birth in a large sample of female twins from the United Kingdom (N = 2,752). We present novel estimates using within–identical twin and biometric models. Our findings show that one year of additional schooling is associated with about one-half year later age at first birth in ordinary least squares (OLS) models. This estimate reduced to only a 1.5-month later age at first birth for the within–identical twin model controlling for all shared family background factors (genetic and family environmental). Biometric analyses reveal that it is mainly influences of the family environment—not genetic factors—that cause spurious associations between education and age at first birth. Last, using data from the Office for National Statistics, we demonstrate that only 1.9 months of the 2.74 years of fertility postponement for birth cohorts 1944–1967 could be attributed to educational expansion based on these estimates. We conclude that the rise in educational attainment alone cannot explain differences in fertility timing between cohorts.     

Father Absence and Accelerated Reproductive Development in Non-Hispanic White Women in the United States

Girls who experience father absence in childhood also experience accelerated reproductive development in comparison with peers with present fathers. One hypothesis advanced to explain this empirical pattern is genetic confounding, wherein gene-environment correlation (rGE) causes a spurious relationship between father absence and reproductive timing. We test this hypothesis by constructing polygenic scores for age at menarche and first birth using recently available genome-wide association study results and molecular genetic data on a sample of non-Hispanic white females from the National Longitudinal Study of Adolescent to Adult Health. We find that young women’s accelerated menarche polygenic scores are unrelated to their exposure to father absence. In contrast, polygenic scores for earlier age at first birth tend to be higher in young women raised in homes with absent fathers. Nevertheless, father absence and the polygenic scores independently and additively predict reproductive timing. We find no evidence in support of the rGE hypothesis for accelerated menarche and only limited evidence in support of the rGE hypothesis for earlier age at first birth.     

高校学生生殖健康、性行为及避孕节育的调查研究

深化研究高校学生生殖健康、性行为及避孕节育具有非常重要的战略意义,通过对北京等七城市各类院校、各年级学生进行调查,分析研究高校学生生殖健康、性行为及避孕节育状况。调查研究内容主要涵盖了三个方面:高校学生生殖健康知识掌握及态度状况;高校学生避孕药具及避孕服务的利用情况;避孕节育服务需求情况。在此基础上,确立和探究了高校学生生殖健康、性行为及避孕节育的导向原则、服务模式及推进措施。     

Environmental quality and fertility: the effects of plant density,species richness,and plant diversity on fertility limitation

The relationship between the environment and population has been of concern for centuries, and climate change is making this an even more pressing area of study. In poor rural areas, declining environmental conditions may elicit changes in family-related behaviors. This paper explores this relationship in rural Nepal looking specifically at how plant density, species richness, and plant diversity are related to women’s fertility limitation behavior. Taking advantage of a unique data set with detailed micro-level environmental measures and individual fertility behavior, I link geographically weighted measures of flora at one point in time to women’s later contraceptive use as a way to examine this complex relationship. I find a significant, positive relationship between plant density, species richness, and plant diversity and the timing of contraceptive use. Women in poor environmental conditions are less likely to terminate childbearing, or do so later, and therefore more likely to have larger families.     

Effects of the timing of marriage and first birth of the spacing of subsequent births

Analyzing data from a fifteen-year follow-up survey of high school students originally surveyed in 1957–58 and resurveyed in 1973–74, this paper examines the effects of the timing of marriage and first birth on subsequent child spacing, holding constant the effects of other variables that may be sources of spuriousness. The results suggest that age at first marriage has a causal effect on the occurrence of a short first birth interval and that age at first marriage and premarital pregnancy interact in their effect on the occurrence of a short second birth interval. Age at first marriage has no causal effect on the spacing of the second birth for those whose first child was maritally conceived. The spacing of the first birth, however, appears to have a causal effect on the spacing of the second.     

Reassessing the link between premarital cohabitation and marital instability

Premarital cohabitation has been found to be positively correlated with the likelihood of marital dissolution in the United States. To reassess this link, I estimate proportional hazard models of marital dissolution for first marriages by using pooled data from the 1988, 1995, and 2002 surveys of the National Survey of Family Growth (NSFG). These results suggest that the positive relationship between premarital cohabitation and marital instability has weakened for more recent birth and marriage cohorts. Using multiple marital outcomes for a person to account for one source of unobserved heterogeneity, panel models suggest that cohabitation is not selective of individuals with higher risk of marital dissolution and may be a stabilizing factor for higher-order marriages. Further research with more recent data is needed to assess whether these results are statistical artifacts caused by data weaknesses in the NSFG.     

Reactions to Blake and Das Gupta’s “the fallacy of the five million women: A re-estimate”

This article reviews the methods used by Blake and Das Gupta (1972) to estimate need for contraceptive protection among single (never-married) and previously married women below the near-poverty line in 1966. More recent data than those used by Blake and Das Gupta to estimate coital activity and protection by contraception allow calculation of alternative estimates of the number of single and previously married women in need in 1966. To assess the relative accuracy of the two estimates, we introduce a validity check. Using vital data from the National Natality Survey and other sources, we calculate a birth rate and a pregnancy rate for low-income single and previously married women, using the two estimates of the number of women in need—i.e., the population at risk of these vital events. If the two estimates of the number in need of contraceptive protection are either excessively low or high, this should be apparent in the resulting birth and pregnancy rates.     

The temporal relationship of marriage,conception, and birth in Massachusetts

An investigation into the timing of first births in relationship to the date of marriage in Massachusetts confirmed the finding of previous national and local birth timing studies that first births likely to have been conceived before the marriage of their parents constitute a substantial proportion of all first births. The differential frequency of premaritally conceived births among various subgroups appeared to account for the variation noted in the overall timing patterns of first births after marriage. Data were gathered through linkage of certificates of birth of a sample of legitimate first children with the marriage record of their parents. Analysis of the marriage-first birth interval by maternal age and race, type of marriage ceremony, and occupation of the bride and groom were conducted and comparisons with previously published data were made. Separate consideration was given to the frequency and characteristics of those births likely to be premaritally conceived and those likely to have been conceived after the wedding.     

Regression analysis of the relationship between the birth rate and proportion of first order births in 1981]

Generally speaking, various fertility indicators such as the birth rate, average fertility rate, and total fertility rate have a close relationship. Various regression analyses have also been made by using different data on population statistics to describe their internal relationships. A regression analysis of the relationship between the birth rate and proportion of first order births, however, has not been made. Data collected by family planning staff at various places show that the places with a high rate of first order births normally have a lower birth rate, and the places with a low rate of first order births very often have a high birth rate. From here we may find that the proportion of the first order births is moving in two opposite directions, and there is no determined relationship between them. It is impossible to use one indicator to calculate the other's indicator. Only a regression analysis can be made to study the relationship between the two. The birth rate and proportion of first order births in 1981 showed some negative relationship, but the use of a regression equation should still be restricted. The regression equation between the birth rate and proportion of first order births may reflect a correct relationship when the region and the number of first order births are fixed. Therefore, any factor which has an impact on the number of first order births also has an influence on the use of regression equation.     

The Quality of Male Fertility Data in Major U.S. Surveys

Researchers continue to question fathers’ willingness to report their biological children in surveys and the ability of surveys to adequately represent fathers. To address these concerns, this study evaluates the quality of men’s fertility data in the 1979 and 1997 cohorts of the National Longitudinal Survey of Youth (NLSY79 and NLSY97) and in the 2002 National Survey of Family Growth (NSFG). Comparing fertility rates in each survey with population rates based on data from Vital Statistics and the U.S. Census Bureau, we document how the incomplete reporting of births in different surveys varies according to men’s characteristics, including their age, race, marital status, and birth cohort. In addition, we use Monte Carlo simulations based on the NSFG data to demonstrate how birth underreporting biases associations between early parenthood and its antecedents. We find that in the NSFG, roughly four out of five early births were reported; but in the NLSY79 and NLSY97, almost nine-tenths of early births were reported. In all three surveys, incomplete reporting was especially pronounced for nonmarital births. Our results suggest that the quality of male fertility data is strongly linked to survey design and that it has implications for models of early male fertility.     

The age at first birth and timing of the second in Costa Rica and Guatemala

This paper explores the relationship between the age at first birth and the timing of subsequent fertility in Costa Rica and in four rural villages and two urban areas of Guatemala. The results indicate that, for Costa Rica, the age at first birth is significantly related to the tempo of subsequent births, and that this association, at least for the interval to second birth, remains significant when socio-economic factors and marital status at the time of first birth are held constant. While the results suggest that the age at first birth is related to timing of the second in the Guatemalan sample as well, the association is weaker and less consistent than in Costa Rica.     

Entering first union: the choice between cohabitation and marriage among women in Italy and Spain

While in Spain and Italy cohabitation has not acquired the same role that it has had in Northern Europe, in both of these Mediterranean countries cohabitation is no longer a marginal phenomenon. Moreover, the nature of cohabiting couples is diverse. According to the most recent FFS data, first cohabitations constitute a temporary arrangement that usually ends in the formalization of the union (marriage), and within 5 years 28.9 % of first cohabitations in Spain and 51.7 % in Italy were transformed into marriages. Within a Western context of changes in union formation patterns, the study of the choice between marriage and cohabitation as first union is of great significance. Is it possible to identify a shared pattern of union formation in Mediterranean countries like Italy and Spain? The purpose of this paper is to examine the choice between cohabitation and marriage as first union (timing, incidence and determinants) using a comparative life course approach. For the analysis of the timing and prevalence, cumulative incidence curves are calculated by birth cohorts and regions; while two semiparametric competing-risks models are estimated for the determinants of first partnership formation (one for each country), considering birth cohort, parental separation, educational attainment, employment status, age at leaving the parental home and birth of a child (the last three time-varying) as independent variables.     

The family formation process among U.S. marriage cohorts

The family formation process is viewed as the progression of women through first marriage, first, subsequent, and last births and is examined for differential patterns of timing in 1930–1969 marriage cohorts. Based on the childbearing histories of approximately 17,000 white women once and still married, extracted from the June 1975 Current Population Survey, the study uses a dynamic model to show the varying importance across cohorts of the first birth interval as an important indicator of the total time spent in childbearing, social background effects in differentiating the timing of the first two births, and of prior birth transitions as affecting subsequent ones.     

Is Maternal and Child Health Service use a Causal Gateway to Subsequent Contraceptive use?: A Multi-Country Study

The purpose of this study is to examine the relationship between MCH service utilization and contraceptive use in five countries: Bolivia, Guatemala, Indonesia, Morocco, and Tanzania. The analysis is carried out at the level of the individual woman, with contraceptive-use status modeled as a function of: (1) the availability, quality, and packaging of MCH and family planning services; (2) community- and individual-level determinants of health service and contraceptive use; and (3) intensity of prior MCH service use. Data for the analysis comes from DHS data on women of reproductive age linked with data from service-availability surveys. We use full-information, maximum-likelihood regression techniques to control for the effects of unobserved heterogeneity that might otherwise bias our estimates. In three of the five countries (Morocco, Guatemala, and Indonesia) the results of the analysis suggest that the intensity of MCH service use is positively associated with subsequent contraceptive use among women, even after controlling for observed and unobserved individual- and community-level factors. This result lends support to the proposition that, at least in the context of these three countries, the intensity of MCH service per se use does have a “causal” impact on subsequent contraceptive use, even after controlling for factors that “predispose” sample women to use health care services.     

Pregnancy avoidance and coital behavior

This study proposes a behavioral model that identifies determinants of coital activity in the context of pregnancy avoidance and assesses the relationships using weekly panel data collected on 300 rural married women in Sri Lanka in 1988. We discuss the utility of the design, which is similar to that of an epidemiological surveillance system, for the measurement of coital behavior and pregnancy risk perceptions. Perceptions of pregnancy risk, spousal agreement on sexual relations, menstrual and lactational status, and cycle timing, all measured daily, are found to influence significantly the probability of coitus on that day. The findings suggest that substantial gains in studying fertility regulation are likely from closer investigation of the behavioral connections between motivation for pregnancy avoidance and coital incidence. Comparison of such panel data with those of cross-sectional sample surveys also provides insights into the validity of measures of coital and contraceptive behavior.