Reproductive and socioeconomic determinants of child survival: Confounded,interactive, and age‐dependent effects

Abstract

Studies of infant and child mortality have evolved to distinguish between two sets of explanatory variables—factors related to reproductive or maternal characteristics and socioeconomic factors, generally described as characteristics of the family or household. Almost all multivariate analyses include variables from each of these two sets, but there has been little consideration of the relationship between them. We examine how these two sets of variables jointly affect mortality. We test first for confounded effects by examining socioeconomic effects while excluding and then including reproductive variables in nested multivariate models. Next, we look for age‐dependent effects among the explanatory variables and find that reproductive and socioeconomic factors affect mortality at differing ages of children. Finally, we examine interactive effects of the two sets of variables. We conclude that the higher mortality observed among the low status groups is not a result of greater concentration of poor reproductive patterns in those groups. Instead, higher status groups probably have more resources available for combating the negative effects of the same high‐risk reproductive patterns.     

Fitness and fertility among Kalahari !Kung

In this paper we develop a model that examines fertility and childhood mortality patterns and their relationship to environmental variables. Interactions among environmental variables can account for different fertility patterns and different mixes of these variables can produce similar patterns of fertility. Our model attempts to quantify the idea that there is a trade-off between producing a few children likely to survive to reproductive age and producing a greater number of children with lower chances for survival. The optimum mix of these strategies depends on environmental characteristics. We use the model to make predictions about fertility and mortality patterns among two Bushmen populations of southern Africa--the Ghanzi and Ngamiland !Kung--using data collected by Harpending in 1967-1968. The results do not support explanations of the low fertilities observed among !Kung Bushmen women, in whom it is thought that fitness is maximized by limiting fertility, and show no relationship between mortality and family size in either !Kung population. Instead, the number of offspring reaching reproductive age in both populations increases as their completed family size increases. We examine the effects of sex, birth order, and paternal investment on mortality. No sex ratio differences and no differences in mortality by sex or birth order are present. Infant mortality among women who married more than once is significantly higher than among women who married once, suggesting that paternal care has a significant effect.     

Demographic behaviour of adults of mixed ethnic ancestry: Jews in Israel

We examine demographic behaviour of Jewish adults of mixed ethnic ancestry, relative to those of the two major Jewish ethnic groups in Israel. Research has shown that for measures of socioeconomic status, such as educational attainment, outcomes for multi-ethnics are in between – and very close to the middle of – those associated with the two major ethnic groups. We find that, in contrast, the marriage and fertility behaviour of multi-ethnic adults is nearly identical to that of the more socially advantaged ethnic group and quite distinct from that of the less advantaged ethnic group. Through multivariate analyses, we explore factors associated with families of origin, including socioeconomic status and cultural indicators of family norms, which are associated with these patterns. We discuss interpretations of our findings.     

Relative contributions of maternal social and biological characteristics to birth weight and gestation among mothers of different childhood socioeconomic status

There has been no reported systematic attempt to quantify the relative unique contribution of multiple social and biologic maternal characteristics to birthweight and gestational time among mothers of differing childhood socioeconomic backgrounds. This issue was examined in 3 nativity cohorts from a population of 766 black prenatal clinic patients in New York City using a series of stepwise hierarchical multiple regression analyses. Different variable sets contributed to birthweight variance in each group, although total variance explained was similar for the 3. Since the foreign-born cohort represented a different higher childhood socioeconomic background, but was similar to the other groups in current socioeconomic status, the differing observed associations of variable sets to birthweight may be related to childhood socioeconomic status. In all groups, social factors show more effect on gestation among those births more than 2500 grams than for smaller babies and thus account for more total explained birthweight variance for births over 2500 grams. Future research is necessary to replicate these results in the general population since this is the 1st study using multivariate techniques to look at social and biological factors associated with birthweight in groups with different childhood social backgrounds.     

Generalized spatial structural equation models

It is common in public health research to have high-dimensional, multivariate, spatially referenced data representing summaries of geographic regions. Often, it is desirable to examine relationships among these variables both within and across regions. An existing modeling technique called spatial factor analysis has been used and assumes that a common spatial factor underlies all the variables and causes them to be related to one another. An extension of this technique considers that there may be more than one underlying factor, and that relationships among the underlying latent variables are of primary interest. However, due to the complicated nature of the covariance structure of this type of data, existing methods are not satisfactory. We thus propose a generalized spatial structural equation model. In the first level of the model, we assume that the observed variables are related to particular underlying factors. In the second level of the model, we use the structural equation method to model the relationship among the underlying factors and use parametric spatial distributions on the covariance structure of the underlying factors. We apply the model to county-level cancer mortality and census summary data for Minnesota, including socioeconomic status and access to public utilities.     

Demographic, social, and economic effects on Mexican causes of death in 1990

This study examined spatial geographic patterns of cause of death and 28 demographic and socioeconomic influences on causes of death for 31 Mexican states plus the Federal District for 1990. Mortality data were obtained from the state death registration system and are age standardized. The 28 socioeconomic variables were obtained from Census records. Analysis included 2 submodels: one with all 28 socioeconomic variables in a stepwise regression, and one with each of the 4 groups of factors. The conceptual model is based on epidemiological transition theory and empirical findings. There are 4 stages in mortality decline. Effects are grouped as demographic, sociocultural, economic prosperity, and housing, health, and crime factors. Findings indicate that cancer and cardiovascular disease were strongly correlated and consistently high in border areas as well as the Federal District and Jalisco. Respiratory mortality had higher values in the Federal District, Puebla, and surrounding states, as well as Jalisco. The standardized total mortality rate was only in simple correlations associated inversely with underemployment. All cause specific mortality was associated with individual factors. Respiratory mortality was linked with manufacturing work force. Cardiovascular and cancer mortality were associated with socioeconomic factors. In submodel I, cause specific mortality was predicted by crowding, housing characteristics, marriage and divorce, and manufacturing work force. In submodel II, economic group factors had the strongest model fits explaining 33-60% of the "r" square. Hypothesized effects were only partially validated.     

Racial/Ethnic Differences in Early-Life Mortality in the United States

U.S. early-life (ages 1–24) deaths are tragic, far too common, and largely preventable. Yet demographers have focused scant attention on U.S. early-life mortality patterns, particularly as they vary across racial and ethnic groups. We employed the restricted-use 1999–2011 National Health Interview Survey–Linked Mortality Files and hazard models to examine racial/ethnic differences in early-life mortality. Our results reveal that these disparities are large, strongly related to differences in parental socioeconomic status, and expressed through different causes of death. Compared to non-Hispanic whites, non-Hispanic blacks experience 60 percent and Mexican Americans 32 percent higher risk of death over the follow-up period, with demographic controls. Our finding that Mexican Americans experience higher early-life mortality risk than non-Hispanic whites differs from much of the literature on adult mortality. We also show that these racial/ethnic differences attenuate with controls for family structure and especially with measures of socioeconomic status. For example, higher mortality risk among Mexican Americans than among non-Hispanic whites is no longer significant once we controlled for mother’s education or family income. Our results strongly suggest that eliminating socioeconomic gaps across groups is the key to enhanced survival for children and adolescents in racial/ethnic minority groups.     

Changing determinants of infant and child mortality: on the basis of the Korean experience, 1955-73

Data from the 1974 Korean National Fertility Survey were analyzed to learn more about the main determinants of infant and child mortality in the course of mortality decline and how they change. In the Korean survey, about 5000 eligible women were selected for the individual survey and the sample design aimed at a self-weighting nationally representative and probability sample. Preliminary analysis showed clear mortality differentials between different socioeconomic levels and between demographic subgroups in infant and child mortality during the period 1955-73 in Korea. To examine the net effect of each variable on mortality, the logit-linear model was used. A table shows the probability level of 4 variables -- maternal age, birth order, mother's education, and number of rooms used by household -- in Korea, when the effects of others were controlled. In the urban areas, only the socioeconomic factors were the main determinants of infant mortality on all the birth cohorts. Mother's education and number of rooms used strongly affected infant mortality in the 1955-59 and 1960-64 birth cohorts, but the effects became weaker in the 1965-69 and 1970-73 birth cohorts, and their statistical significance was reduced. In the rural areas, the effects of 3 variables -- the exception being number of rooms used -- on infant mortality were statistically significant. It is concluded that the main determinants of infant mortality in urban areas were socioeconomic factors. The main determinants of infant mortality in the rural areas were demographic in the earlier birth cohorts, but in the recent birth cohorts mother's education, a socioeconomic factor, became the main determinant while the effects of demographic variables became weaker and finally disappeared. The change in the determinants of child mortality appears to be the reverse of that for infant mortality. Prior to the introduction of the national development program, in the rural areas mother's education was the main determinant of child mortality (rural 1955-59 cohort), but with the socioeconomic development the determinants changed to give dominance to demographic factors (urban 1955-59) cohort and, in the recent period, even the effects of demographic factors on child mortality became weaker (urban 1960-69 cohort). When the differences in living status by maternal age were weaker and the competition among siblings less because of small family size, only the socioeconomic variables remained as main determinants affecting child mortality.     

Social epidemiology of chronic liver disease and cirrhosis mortality in the United States, 1935-1997: trends and differentials by ethnicity, socioeconomic status, and alcohol consumption

This study examines trends and ethnic and socioeconomic differentials in chronic liver disease and cirrhosis mortality in the United States. Age-adjusted death rates from the National Vital Statistics System were used to analyze race and sex-specific mortality trends from 1968 through 1997. Age-adjusted liver cirrhosis mortality and per capita alcohol consumption data from 1935 through 1996 were modeled using time-series regression. Moreover, the Cox hazards regression was applied to the National Longitudinal Mortality Study, 1979-1989, to examine socioeconomic differentials at the individual level, whereas multivariate ordinary least squares regression was used to model state-specific cirrhosis mortality from 1990 to 1992 as a function of socioeconomic variables and alcohol consumption at the ecological level. Chronic liver disease and cirrhosis continues to be an important cause of death in the United States, even after three decades of consistently declining mortality rates. For both men and women aged 25 years and older, significant mortality differentials were found by age, race/ethnicity, marital status, family income, and employment status. For men, marked differentials were also found by nativity, rural-urban residence, and education. Unemployment, minority concentration, and alcohol consumption were major predictors of state-specific cirrhosis mortality. Both time-series and cross-sectional data indicate a strong correlation between alcohol consumption and US cirrhosis mortality. Substantial ethnic and socioeconomic differences in cirrhosis mortality suggest the need for social and public health policies and interventions that target such high-risk groups as American Indians, Hispanic Americans, the socially isolated, and the poor.     

Deformed nasal septa and relaxed selection

Abstract

Demographic studies undertaken in several Andean countries have found that women residing at high altitudes have significantly fewer live births than do their low altitude counterparts. This reduction has been explained as being due to various factors: the debilitating effects of hypoxia upon the reproductive system; the effects of sociocultural factors which vary with altitude and which affect reproductive behavior; and errors in data collection. In order to examine the validity of some of these hypotheses, the fertility of a group of 906 Bolivian women residing at low, medium, and high altitudes was examined. The women were selected from the lower socioeconomic strata and reported never having used any method of contraception. A detailed analysis of the fertility of these women showed no significant altitude‐related differences in the number of live births. However, as a result of significantly higher childhood mortality rates at altitude, there was a significant reduction in numbers of living children. The results of this study suggest that the collection and analysis of census data that ignores socioeconomic differences within a population or differences among census units in neonatal or early childhood mortality may bias or complicate the study of the impact of altitude on human fertility. Although the present research does not prove that hypoxic stress does not affect the reproductive system, the results suggest that if altitude does reduce fecundity, the reduction is not great and is likely to be shown only through studies of reproductive physiology.     

Relative Contributions of Geographic,Socioeconomic, and Lifestyle Factors to Quality of Life,Frailty, and Mortality in Elderly

Background

To date, few studies address disparities in older populations specifically using frailty as one of the health outcomes and examining the relative contributions of individual and environmental factors to health outcomes.

Methodology/Principal Findings

Using a data set from a health survey of 4,000 people aged 65 years and over living in all regions of Hong Kong, we examined regional variations in self-rated health, frailty, and four-year mortality, and analyzed the relative contributions of lifestyle, socioeconomic status, and geographical location of residence to these outcomes using path analysis. We hypothesize that lifestyle, socioeconomic status, and regional characteristics directly and indirectly through interactions contribute to self-rated physical and psychological health, frailty, and four-year mortality.District variations directly affect self-rated physical health, and also exert an effect through socioeconomic position as well as lifestyle factors. Socioeconomic position in turn directly affects self-rated physical health, as well as indirectly through lifestyle factors. A similar pattern of interaction is observed for self-rated mental health, frailty, and mortality, although there are differences in different lifestyle factors and district associations. Lifestyle factors also directly affect physical and mental components of health, frailty, and mortality. The magnitude of direct district effect is comparable to those of lifestyle and socioeconomic position.

Conclusions/Significance

We conclude that district variations in health outcomes exist in the Hong Kong elderly population, and these variations result directly from district factors, and are also indirectly mediated through socioeconomic position as well as lifestyle. Provision and accessibility to health services are unlikely to play a significant role. Future studies on these district factors would be important in reducing health disparities in the older population.     

Relative contributions of maternal social and biological characteristics to birth weight and gestation among mothers of different childhood socioeconomic status

Abstract

There has been no reported systematic attempt to quantify the relative unique contribution of multiple social and biologic maternal characteristics to birth weight and gestational time among mothers of differing childhood socioeconomic backgrounds. We examined this issue in three nativity cohorts from a population of 766 black prenatal clinic patients in New York City using a series of stepwise hierarchical multiple regression analyses. Different variable sets contributed to birth weight variance in each group, although total variance explained was similar for the three. Since the foreign‐born cohort represented a different higher childhood socioeconomic background, but was similar to the other groups in current SES, the differing observed associations of variable sets to birth weight may be related to childhood socioeconomic status. In all groups, social factors show more effect on gestation among births more than 2,500 grams than for smaller babies and thus account for more total explained birth weight variance for births over 2,500 grams.     

Urban Morphology Drives the Homogenization of Tree Cover in Baltimore,MD, and Raleigh,NC

Heterogeneous land cover patterns contribute to unique ecological conditions in cities and little is known about the drivers of these patterns among cities. We studied tree cover patterns in relationship to urban morphology (for example, housing density, parcel size), socioeconomic factors (for example, education, income, lifestyle characteristics), and historical legacies in Baltimore, Maryland, and Raleigh, North Carolina. Utilizing a multimodel inference approach and bivariate analyses, we analyzed two primary datasets employed in previous research predicting urban tree cover—one comprising continuous data (US Census), and the other consisting of categorical variables (Claritas PRIZM) that incorporate consumer purchasing data. Continuous data revealed that urban morphological characteristics were better predictors of tree cover patterns than socioeconomic factors in Raleigh and Baltimore at the parcel and neighborhood scales. Although the categorical dataset provided some evidence for the importance of socioeconomic and lifestyle characteristics in predicting tree cover patterns, the hierarchical nature of these data preclude separating the impacts of these factors from levels of urbanization. Bivariate analyses of continuous and categorical variables revealed that the highest correlation coefficients were associated with variables describing urban morphology—parcel size, percent pervious area, and house age. In Baltimore, historical census data were better predictors of present-day tree cover than census data from recent years. Most notably, parcel size, a key predictor of tree cover, has decreased with time in Raleigh to sizes consistently seen in Baltimore. Our findings demonstrate that urban morphology, the main driver of tree cover patterns in these cities, may lead to the homogenization of tree canopy in Raleigh and Baltimore in the future.     

Humidity levels drive reproductive modes and phylogenetic diversity of amphibians in the Brazilian Atlantic Forest

Aim The diversity of reproductive modes among amphibians constitutes a striking example of how differences in the biology of species provide important explanations for species distribution patterns on a broad scale. We hypothesize that sites with a higher humidity level will support more modes of reproduction than drier sites and will consequently exhibit a higher phylogenetic diversity. Furthermore, if there is a gradient in the tolerance of reproductive modes to desiccation, there will be a nested pattern in the composition of reproductive modes among sites. Location Twenty‐seven forest sites in the Brazilian Atlantic Forest. Methods Through a path analysis approach, we evaluated the direct and indirect effects of the humidity level on the number of reproductive modes, as well as the relative importance of both variables on amphibian phylogenetic diversity. A nestedness analysis was used to quantify the extent to which the compositions of both species and reproductive modes in drier sites correspond to subsets of those in sites with higher annual precipitation. Results We found that the reproductive modes present in drier sites are non‐random subsets of those present in sites with higher humidity levels. Because reproductive modes are phylogenetically conserved among amphibians, sites with a greater number of reproductive modes supported greater phylogenetic diversity. Sites with high precipitation throughout the year provided suitable environmental conditions for a larger number of reproductive modes, whereas sites with low precipitation and typical seasonal climates supported only those reproductive modes specialized to resist desiccation. Main conclusions Our results show that humidity‐related variables are key environmental factors related to both the richness of reproductive modes and phylogenetic diversity. Our results support the hypothesis that the higher phylogenetic diversity found in moister sites reflects differences in the tolerance to desiccation among different reproductive modes. Given that reproductive modes are associated with susceptibility to desiccation, their incorporation into explanatory models may trigger a significant advance in the understanding of the mechanisms regulating the species richness and composition of amphibian communities.     

Determinants of infant and early childhood mortality in Cameroon: The role of socioeconomic factors,housing characteristics,and immunization status

Abstract

This study examines factors impinging on the survival of children in Cameroon using longitudinal data collected by the United Nations Demographic Training and Research Institute of Yaounde, Cameroon. It deals especially with the role of socioeconomic factors (mother's education, employment, marital status, ethnicity, and household income), housing characteristics (construction materials, power source, source of water supply, extent of crowding), and immunization status on infant and child mortality. Two‐state parametric and nonparametric hazards models for the risk of death at any time within the course of the study are used, with and without accounting for unmeasured heterogeneity. Overall, overcrowding has robust deleterious effects on infant and child survival. As regards the effects of socioeconomic variables, the robustness of the effects of household income and ethnic differentials are unchanged, even after controlling for unmeasured heterogeneity; the deleterious effects of marital status are also apparent, but these effects are largely explained by unmeasured covariates. The data also suggest that the protective effects of full immunization status are robust and not contaminated by confounding factors, at least in the first 16 months of life. These findings provide solid ground to support immunization programs and efforts as a means to reduce significantly infant and child mortality.     

Catching up from early nutritional deficits? Evidence from rural Ethiopia

We examine the nutritional status of a cohort of poor Ethiopian children and their patterns of catch-up growth in height-for-age between three key development stages: age one, five and eight. We use ordinary least squares (within community) and instrumental variables analysis. During the earliest period, we find that nutritional catch-up patterns vary substantially across socioeconomic groups: average catch-up growth in height-for-age is almost perfect among children in relatively better-off households, while among the poorer children, relative height is more persistent. Between five and eight years of age, however, we find near-perfect persistence and no evidence of heterogeneity in catch-up growth. Our findings suggest that household wealth, and in particular access to services, can lead to substantial catch-up growth early on in life. However, for our sample, the window of opportunity to catch up appears to close as early as the age of five.     

The Effects of Socioeconomic Status,Clinical Factors,and Genetic Ancestry on Pulmonary Tuberculosis Disease in Northeastern Mexico

Diverse socioeconomic and clinical factors influence susceptibility to tuberculosis (TB) disease in Mexico. The role of genetic factors, particularly those that differ between the parental groups that admixed in Mexico, is unclear. The objectives of this study are to identify the socioeconomic and clinical predictors of the transition from latent TB infection (LTBI) to pulmonary TB disease in an urban population in northeastern Mexico, and to examine whether genetic ancestry plays an independent role in this transition. We recruited 97 pulmonary TB disease patients and 97 LTBI individuals from a public hospital in Monterrey, Nuevo León. Socioeconomic and clinical variables were collected from interviews and medical records, and genetic ancestry was estimated for a subset of 142 study participants from 291,917 single nucleotide polymorphisms (SNPs). We examined crude associations between the variables and TB disease status. Significant predictors from crude association tests were analyzed using multivariable logistic regression. We also compared genetic ancestry between LTBI individuals and TB disease patients at 1,314 SNPs in 273 genes from the TB biosystem in the NCBI BioSystems database. In crude association tests, 12 socioeconomic and clinical variables were associated with TB disease. Multivariable logistic regression analyses indicated that marital status, diabetes, and smoking were independently associated with TB status. Genetic ancestry was not associated with TB disease in either crude or multivariable analyses. Separate analyses showed that LTBI individuals recruited from hospital staff had significantly higher European genetic ancestry than LTBI individuals recruited from the clinics and waiting rooms. Genetic ancestry differed between individuals with LTBI and TB disease at SNPs located in two genes in the TB biosystem. These results indicate that Monterrey may be structured with respect to genetic ancestry, and that genetic differences in TB susceptibility in parental populations may contribute to variation in disease susceptibility in the region.     

Spatial factors affecting primary succession on the Muddy River Lahar,Mount St. Helens,Washington

Primary succession is controlled by a combination of landscape and habitat factors whose actions may be stochastic or deterministic. The 1980 eruption of Mount St. Helens, Washington spawned a massive lahar that now supports a mosaic of vegetation. Our goals were to describe vegetation patterns after 28 growing seasons, determine the factors associated with these patterns, and to contrast the effects of stochastic and deterministic processes. We described species composition and explanatory factors that included location and habitat features in one hundred and fifty one 200-m² plots. We classified these plots into nine community types (CTs) that were distinguished quantitatively by variations in dominant species. We used multiple regressions, redundancy analysis (RDA), and Mantel tests to compare the vegetation relationships with explanatory factors. Plots in different CTs mingled spatially and in multivariate space. Species patterns were weakly related to explanatory variables by RDA (31.6% of the species variation). RDA indicated that vegetation was most strongly related to elevation, latitude, and isolation, which are primarily landscape factors. Mantel tests confirmed that factors associated with elevation were most closely associated with vegetation. The effects of arrival order were suggested by the dominance of different colonizers in similar environment and by plots with similar vegetation found in different habitats. We concluded that species composition cannot be predicted well from the data available, suggesting that there were no prominent deterministic assembly rules.     

Geohistorical and current environmental influences on floristic differentiation in the Ryukyu Archipelago, Japan

Aim Floristic differentiation in the Ryukyu Archipelago has been explained primarily by geohistory, specifically landbridge formation and vicariance at the Tokara and Kerama Gaps, two deep‐sea channels through the island arc. This ignores current environmental effects, which may also be important. We therefore tested whether the floristic differentiation pattern is explained primarily by the historical effect of the gaps as barriers, or whether a better understanding of floristic differentiation is achieved when both historical and current environmental factors are incorporated. Location Ryukyu Archipelago, Japan: an assemblage of continental islands. Methods We compiled a presence–absence matrix of 1815 plant species on 26 islands. Floristic dissimilarity distances between islands were calculated using Simpson’s similarity index and analysed using cluster analysis. We also conducted multiple regression on distance matrices (MRM) to examine the significance of the historical factors of the gaps and current environmental factors: geographical distance among islands and differences in island area and maximum elevation. Results We detected clear patterns of floristic differentiation across the gaps. Using the two gaps as explanatory variables, the MRM showed that both had significant effects on floristic dissimilarity distance. However, when geographical distance was added to the explanatory model, the Kerama Gap effect disappeared. When all five explanatory variables were used, the Tokara Gap and geographical distance had positive effects, but area difference had a negative effect. The Kerama Gap and difference in maximum elevation had no effect. Main conclusions The geographical pattern of floristic differentiation appears to indicate the influence of both gaps. However, the MRM indicates that the floristic differentiation across the Kerama Gap is no more than could be explained solely by geographical distance. Across the Tokara Gap, however, floristic differentiation is larger than geographical distance alone can explain. This additional differentiation is attributable to the effect of the historical barrier. To verify the significance of historical effects of vicariance on island biota, the confounding effects of geographical distance must be considered. The distance decay of floristic similarity and negative effect of area difference on floristic differentiation demonstrate that floristic differentiation is better understood by incorporating both historical and current environmental factors.     

Age of mother and pregnancy outcome in the 1981 Arkansas birth cohort

Higher levels of obstetric risk observed among teenage mothers seem to be an artifact of lower socioeconomic status and inferior access to health care rather than biological immaturity. In a study of matched Arkansas birth-infant death records for 1978, the proxy variables for health access (month care started and number of visits) have the strongest association with each of the dependent variables. The indicators of social status (education, race, and marital status) have a weaker association, and there is virtually no age effect observable once the affects of socioeconomic status and health access have been controlled for. A series of stepwise regression analyses shows that the multiple partial for health access indicators and mortality is 0.036, while the same coefficients for social status indicators and age are 0.001 and 0.006, respectively. Similar results are obtained using the other dependent variables. Health consequences of adolescent pregnancy usually include higher rates of malnutrition and prematurity and lower birth weight. It seems that the elevated morbidity and mortality among newborns delivered by teenagers are not a result of biologic factors. After the effects of lower status and health care access have been removed, the apparent biological disadvantages attributed to teenagers disappear, and, in the case of mortality and birth weight, are replaced by a slight advantage. This advantage is observed through the use of statisitical controls and will not be observed in the population at large unless there are changes in the policies governing access to contraception, abortion, and health care by adolescents, especially those at the youngest ages.