Application of life table techniques to measurement of contraceptive effectiveness

Two problems are associated with the analysis of use-effectiveness of contraception. First, couples belonging to a sample of contraceptors typically vary in their monthly chances of contraceptive failure. Second, one does not observe for many, and perhaps a majority of the couples, how long they can remain protected with the contraceptive, because either they are stopping contraception to plan a pregnancy or else observation of them is being interrrupted by lost contact, by discontinuation of contraception for other reasons, or by the end of the study. It is argued that because of these two problems-namely, sample heterogeneity and incomplete histories-the Pearl pregnancy rate, which has been traditionally used to measure contraceptive effectiveness, is inadequate.A life table method is described that permits one to combine incomplete histories with complete ones for purposes of estimating the proportions of the sample that might have remained protected for specified periods if all members had remained under observation for these periods. The versatility of the techniques is illustrated in relation toa retrospective survey. A detailed account of procedure is given. Finally, it is shown that only under specialized conditions that are rarely met in practice is it possible to estimate the results of the new technique from knowledge of Pearl pregnancy rates alone.     

The demographic effects of a contraceptive programme

Abstract The calculation of the number of births prevented for each item of contraceptive service provided entails the integration of a variety of factors relating to the potential fertility of users and the duration and effectiveness of use. This article differs from previous essays of this kind in that estimates of future potential fertility are based not on fertility rates but on age-specific means of inter-live birth intervals, modified by periods of use overlapping post-partum sterility, and by the probabilities attached to the development of permanent sterility and to the successful adoption of extra-programme birth control. In the first three years after acceptance of intra-uterine contraception by some 9,000 postpartum women of several ethnic origins in Singapore, it is calculated that about 4,800 births were prevented.     

The contribution of HIV to fertility decline in rural Zimbabwe, 1985-2000

HIV-related sub-fertility has been reported for those populations in sub-Saharan Africa in which contraceptive use is low. We use data from a retrospective survey in rural Zimbabwe and multivariate logistic regression models to show that recent birth rates and current pregnancy rates are also lower among HIV-positive women than among HIV-negative women in those African populations where contraceptive use is high. The fertility reduction is smaller than where contraceptive use is low because age at first sexual intercourse is later and birth rates at older ages are already low. Nevertheless, total fertility is approximately 8.5 per cent lower and HIV-associated sub-fertility may account for as much as one-quarter of fertility decline in Zimbabwe since the late 1980s. Mechanisms for HIV-associated sub-fertility in rural Zimbabwe include more frequent widowhood and divorce, reduced coital frequency, increased amenorrhoea, and possibly, pelvic inflammatory disease. Miscarriage appears to be a less important factor than elsewhere possibly because syphilis is rare.     

Effect of provider characteristics on choice of contraceptive provider: A two-equation full-information maximum-likelihood estimation

We use surveys of households and health-care facilities conducted in the same area at the same time to determine which characteristics of providers attract users of contraceptives. By using the full-information maximum-likelihood technique to jointly estimate choice of contraceptive method and choice of provider, we avoid self-selection bias. Results support the need for modeling quality and for jointly estimating the choice of contraceptive method and the choice of provider to avoid biased estimates of coefficients. The results suggest that for the Cebu, Philippines region, small local clinics that focus on family planning tend to be most favored by clients.     

Is breast-feeding a substitute for contraception in family planning?

Using data from the Cebu Longitudinal Health and Nutrition Survey, I disentangle the complex interrelationship between breast-feeding, postpartum amenorrhea, and choice of contraceptive method. I find evidence that women substitute breast-feeding for contraception. Further, endogeneity bias, if not controlled, would cause the relationship to be slightly overstated. In addition, the results suggest that although increased education and income result in decreased breast-feeding, any effect on fertility will be offset by changes in contraceptive use.     

Analysis of oral contraceptive use through multiple decrement life table techniques

Multiple decrement life table technique is used to analyze the oral contraceptive use in a sample of once married women in Metropolitan Toronto. The overall pattern in the Canadian data is found to be essentially similar to that found in the U. S. Continuation rates show differences by cause of decrement. Two types of rates, net and absolute, are presented, and the relationship between single decrement continuation rates and total continuation rates is examined. Some problems of clinical versus retrospective sample survey data in studies of contraceptive effectiveness are commented on.     

Target Fertility,Contraception, And Aggregate Rates: Toward A Formal Synthesis

This paper develops a stock adjustment model relating total expected births to conventional aggregate fertility rates for married women over 25. Each year, cohorts bear about 20 percent of their additional expected births. Aggregate U.S. rates have been consistent with expectations as expressed in surveys between 1955 and 1975; indeed, total expected births may be inferred from aggregate fertility behavior. A peculiar empirical finding is that the additional expected fertility of nonterminators has not changed since 1955, despite the dramatic decline in total expected and actual fertility. The model leads to a dynamic expression for the duration pattern of current and cumulative fertility and for the proportion of couples who have terminated childbearing. The model is also used to analyze the effects of changing contraceptive failure rates on fertility patterns. For example, a decline in “timing” failure rates increases duration-specific fertility five years later.     

基于整体网络视角的农民工避孕行为影响因素分析

本文采用2005年“深圳市外来农村流动人口调查”数据,利用社会网络分析方法从整体网络角度定量研究了农民工避孕行为的影响因素。利用p*模型从整体网络结构特征分析表明,不同层次的关系结构变量对农民工是否讨论避孕的影响不同,多数个体层次变量对是否讨论避孕有显著影响;本文从整体网络衍生出个体网络,并从衍生个体网络角度研究表明,网络规模和网络成员的避孕措施会对农民工避孕措施多元化有较为显著影响。     

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.     

Sampling Weights for Analyses of Couple Data: Example of the Demographic and Health Surveys

In some surveys, women and men are interviewed separately in selected households, allowing matching of partner information and analyses of couples. Although individual sampling weights exist for men and women, sampling weights specific for couples are rarely derived. We present a method of estimating appropriate weights for couples that extends methods currently used in the Demographic and Health Surveys (DHS) for individual weights. To see how results vary, we analyze 1912 estimates (means; proportions; linear regression; and simple and multinomial logistic regression coefficients, and their standard errors) with couple data in each of 11 DHS surveys in which the couple weight could be derived. We used two measures of bias: absolute percentage difference from the value estimated with the couple weight and ratio of the absolute difference to the standard error using the couple weight. The latter shows greater bias for means and proportions, whereas the former and a combination of both measures show greater bias for regression coefficients. Comparing results using couple weights with published results using women’s weights for a logistic regression of couple contraceptive use in Turkey, we found that 6 of 27 coefficients had a bias above 5 %. On the other hand, a simulation of varying response rates (27 simulations) showed that median percentage bias in a logistic regression was less than 3 % for 17 of 18 coefficients. Two proxy couple weights that can be calculated in all DHS surveys perform considerably better than either male or female weights. We recommend that a couple weight be calculated and made available with couple data from such surveys.     

Regional variation in acceptance of Indonesia's family planning program

Indonesia's family planning program is regarded as a major success.Survey data from 1997 reveal that rates of contraceptive use vary dramatically amongIndonesia's 27 provinces, from a high of 67 percent of ever married women currently using contraceptives in the province of North Sulawesi, to a low of 19 percent current users in East Timor and28 percent in Aceh. This study uses both a quantitative analysis of the 1997 Indonesia Demographic and Health Survey, and a qualitative study carried out in July of 2000 to understand regionalvariation. The study identified a small number of factors that show a clear relation with levels of contraceptive use. Media exposure and education are the strongest and most consistent predictors of levels of contraceptive use, and appear to be the surest strategies for promoting family change. But the study also showed that the process of social change is subjectto culturally and historically specific local factors whose presence and importance is difficult to predict. Our study of regional variation in contraceptive use illustrates the range and complexityof obstacles faced by Indonesia's leaders in attempting to forge a single nation fromsuch a diverse and far-flung population. Although the creation of Indonesia in the space of just half a century is a monumental achievement, the project is clearly not yet complete.     

Attitudes About Children and Fertility Limitation Behavior

The relationship between attitudes and individual behavior is at the core of virtually all demographic theories of fertility. This paper extends our understanding of fertility behavior by exploring how psychic costs of childbearing and contraceptive use, conceptualized as attitudes about children and contraception, are related to the transition from high fertility and little contraceptive use to lower fertility and wide spread contraceptive use. Using data from rural Nepal, I examine models of the relationship between multiple, setting-specific attitudes about children and contraception and the hazard of contraceptive use to limit childbearing. Specific attitude measures attempt to capture the relative value of children versus consumer goods, the religiously based value of children, and the acceptability of contraceptive use. Findings demonstrate that multiple measures of women’s attitudes about children and contraception were all independently related to their fertility limitation behavior.     

Impact of having a high-risk pregnancy on future postpartum contraceptive method choice

BackgroundTo compare the knowledge and preference of preconceptional contraception to future postpartum contraceptive method choice in high-risk pregnancies.Research questionDoes a high-risk pregnancy condition affect future postpartum contraceptive method choice?MethodWomen hospitalised at the High Risk Pregnancy unit of a tertiary research and training hospital were asked to complete a self-reported questionnaire that included demographic characteristics, presence of unintended pregnancy, contraceptive method of choice before the current pregnancy, plans for contraceptive use following delivery and requests for any contraceptive counselling in the postpartum period.FindingsA total of 655 pregnant women were recruited. The mean age, gravidity and parity of the women were 27.48 ± 6.25 years, 2.81 ± 2.15 and 1.40 ± 1.77, respectively. High-risk pregnancy indications included 207 (31.6%) maternal, 396 (60.5%) foetal and 52 (7.9%) uterine factors. All postpartum contraceptive choices except for combined oral contraceptives (COCs) usage were significantly different from preconceptional contraceptive preferences (p < 0.001). High-risk pregnancy indications, future child bearing, ideal number of children, income and education levels were the most important factors influencing postpartum contraceptive choices. While the leading contraceptive method in the postpartum period was long-acting reversible contraceptive methods (non-hormonal copper intrauterine device Cu-IUD, the levonorgestrel-releasing intrauterine system (LNG-IUS) (40%), the least preferred method was COCs use (5.2%) and preference of COCs use showed no difference between the preconceptional and postpartum periods (p = 0.202). Overall 73.7% of the women wanted to receive contraceptive counselling before their discharge.ConclusionA high-risk pregnancy condition may change the opinion and preference of contraceptive use, and also seems to affect the awareness of family planning methods.     

Why the rise in adolescent fertility rates in the Dominican Republic in the 1990s?

Despite concern over high pregnancy rates and levels of risk for sexually transmittedinfections, adolescent fertility rates in the Dominican Republic have not changed substantially since the early 1980's, and actually increased during the early to mid 1990s. The present study was undertaken to assess the factors contributing to the recent rise in fertility among Dominican adolescents. The findings suggest that although contraceptive use among adolescents and young adults has increased, this has been more than offset by ominous trends on other determinants of fertility. Among these are declines in mean age at first sex and first marriage/union without a commensurate decline in mean age at first contraceptive use, and stubbornly high discontinuation rates for oral contraceptives andcondoms. There is also some evidence that rates of induced abortion among adolescents may have increased, without which adolescent fertility rates would have been even higher. Demand for children among Dominican adolescents remains strong, suggesting that efforts to reduce the current high prevalence of risky sexual behaviors need to influence social norms in order to be successful.     

The role of contraceptive supply and demand in Mexican fertility decline: evidence from a microdemographic study

This paper uses retrospective life history data to assess the impact of family planning services on contraceptive use in a rural Mexican township. Between 1960 and 1990 contraceptive use rose and fertility declined dramatically. Both contraceptive supply and demand factors were influential in these trends. The start of the government-sponsored family planning programme in the late 1970s was associated with a sharp rise in female sterilization and use of the IUD. However, once we controlled for the changing socio-economic and demographic characteristics of the sample, the presence of family planning services had no significant effect on the likelihood that women used modern reversible methods compared to traditional methods. Men and women expressed concerns about the safety of modern methods such as the pill and the IUD. Efforts to increase modern contraceptive use should place greater emphasis on communicating the safety of these methods and improving the quality of services.     

Appropriate methods for analyzing the effect of method choice on contraceptive discontinuation

The contraceptive method chosen is an important determinant of contraceptive discontinuation. However, method choice is endogenous to contraceptive discontinuation. Using data from the 1997 Indonesia Demographic and Health Survey, we apply a multilevel multi-process model to examine the impact of method choice on three types of contraceptive discontinuation. We confirm that method choice is endogenous to the processes of contraceptive abandonment and method switching, but not failure. Ignoring the endogeneity of contraceptive choice leads to various biases in the magnitude of estimated effects of method choice on abandonment and method switching, but the general conclusions are robust to these biases.     

The Role of Contraceptive Supply and Demand in Mexican Fertility Decline: Evidence from a Microdemographic Study

This paper uses retrospective life history data to assess the impact of family planning services on contraceptive use in a rural Mexican township. Between 1960 and 1990 contraceptive use rose and fertility declined dramatically. Both contraceptive supply and demand factors were influential in these trends. The start of the government-sponsored family planning programme in the late 1970s was associated with a sharp rise in female sterilization and use of the IUD. However, once we controlled for the changing socio-economic and demographic characteristics of the sample, the presence of family planning services had no significant effect on the likelihood that women used modern reversible methods compared to traditional methods. Men and women expressed concerns about the safety of modern methods such as the pill and the IUD. Efforts to increase modern contraceptive use should place greater emphasis on communicating the safety of these methods and improving the quality of services.     

Does Contraceptive Use Always Reduce Breast-feeding?

Previous studies suggest that access to modern contraceptives can reduce breast-feeding rates because women who had been using breast-feeding to avoid pregnancy substitute away from it. This article shows that contraceptive use can also have a positive effect on breast-feeding. A mother often weans a child if she becomes pregnant again, which can occur sooner than desired if she lacks access to contraceptives. Thus, by enabling longer birth spacing and preventing unwanted pregnancies, contraceptive use allows for a longer duration of breast-feeding. This positive effect should primarily affect infants who are past the first few months of life because their mothers are more fecund then, and the negative effect should affect infants who are very young because the contraceptive property of breast-feeding is strongest then. I test for these dual effects using Demographic and Health Survey data for Indonesia. I find evidence of the positive birth-spacing effect: contraceptive use increases the likelihood that children continue to be breast-fed past age 1. There is also suggestive evidence of a negative substitution effect among infants age 3 months and younger.     

Determinants of fertility and the unmet need for family planning in Indonesia

Indonesia's fertility has declined to an average of slightly more than 3 children/woman. The islands of Java and Bali have the lowest birth rates. Indonesia's family planning program has been a model of innovation, flexibility, and community involvement, and has been effective in reducing fertility, changing family preferences, and increasing contraceptive use. Fertility decline is also determined by factors other than contraceptive use, as provinces in Jakarta and East Java has low fertility and low contraceptive use. Recent research by Suyono and Palmore found that among cohorts of women in Jakarta lowest fertility rates were explained by greater nonexposure to pregnancy in an unmarried state or by a divorced or widowed status, and by infecundity. In East Java, fertility determinants were the same with the possible addition of lower coital frequency. The study estimated nonexposure due to marriage, infecundity, and contraceptive use. Policy considerations, however, are concerned with the exposed state of the percentage of time women are currently married, fecund, not using contraceptive, and sexually active. Suyono and Palmore also calculated the percentage of time spent in the exposed state by province. The estimates ranged from 12% in Yogyakarta to 25% in West Java and the Outer Islands. Exposed was further divided into groups with a manifest, latent, and no current need. Women with a manifest need for family planning are those who are aware of their contraceptive needs to stop or postpone childbearing and not using. Manifest need was highest in high fertility areas: 12% in Central Java, 13% in West Java, and 12% in the Outer Islands. Programs targeting these women should focus on wider availability of information and services. Women with latent needs are unaware of their need for family planning and are not using contraception. These women were also concentrated in high fertility areas. The percentage of years spent in the latent unmet need state was estimated at 23-24% in West Java and the Outer Islands. Program emphasis should be on education and motivation to show how family size can be controlled. Women with current need can be educated toward future acceptance.     

Determinants of contraceptive switching behavior in rural Sri Lanka

This study examines the influence of a selected set of determinants of contraceptive method switching in rural Sri Lanka. Of interest is the question of how change in contraceptive practice at the individual level can account for patterns observed at the aggregate level. Based on calendar data on contraceptive use over a 3-year period, collected for more than 3,000 married women in a 1986 survey, the multivariate analysis shows that women who attain all or a significant proportion of their desired fertility tend to switch to more effective methods. Women who experience method failure tend to switch methods, usually to a type that is more effective. The woman's background determinants of age and education have small but significant effects on method switching, whereas the effect of household economic well-being is not significant. There is strong indication that rural couples are practicing contraception in a nonrandom fashion, switching methods in accordance with changes in their fertility motivations and contraceptive experience.