Registration completeness and international comparisons of infant mortality

The physical development of the live born infant is the single most important variable governing its survival: infant mortality among those weighing 2,500 grams (5 1/2 pounds) or less at birth is 17 times the mortality among those weighing more than 2,500 grams at birth. The variation in mortality according to birth weight (or gestation) is greater than for subclasses of color, sex, maternal age, or birth order. Infant mortality in the United States is significantly higher than in a number of other countries e.g., Sweden, Netherlands, Norway. The difference is thought, by some, to be due to underregistration of low birth weight infants in other countries. In this paper, distributions of live births by birth weight for Denmark, England and Wales, New Zealand, and the United States, and infant mortality data for Denmark and the United States are examined. The data do not support a hypothesis of gross underregistration of live born infants in other countries. The results indicate that some index of physical development (birth weight, gestation, or a combination of both) should be included in any appraisal of infant mortality.     

Birth Intervals and Health in Adulthood: A Comparison of Siblings Using Swedish Register Data

A growing body of research has examined whether birth intervals influence perinatal outcomes and child health as well as long-term educational and socioeconomic outcomes. To date, however, very little research has examined whether birth spacing influences long-term health. We use contemporary Swedish population register data to examine the relationship between birth-to-birth intervals and a variety of health outcomes in adulthood: for men, height, physical fitness, and the probability of falling into different body mass index categories; and for men and women, mortality. In models that do not adjust carefully for family background, we find that short and long birth intervals are clearly associated with height, physical fitness, being overweight or obese, and mortality. However, after carefully adjusting for family background using a within-family sibling comparison design, we find that birth spacing is generally not associated with long-term health, although we find that men born after very long birth intervals have a higher probability of being overweight or obese in early adulthood. Overall, we conclude that birth intervals have little independent effect on long-term health outcomes.     

Race/Ethnicity/Nativity Differentials and Changes in Cause-Specific Infant Deaths in the Context of Declining Infant Mortality in the U.S.: 1989–2001

Using data from the national linked birth/infant death cohort files, we examined race/ethnicity/nativity disparities and changes in infant mortality due to the five leading causes of infant death between 1989 and 2001. Our results indicate substantial decreases in infant mortality from three causes (congenital anomalies, sudden infant death syndrome, and respiratory distress syndrome) for which specific perinatal health innovations emerged or were expanded. However, for these three causes, the relative disparities in infant mortality between infants born to U.S.-born black women as compared to infants of U.S.-born white women increased following the introduction (or expansion) of beneficial interventions. Among infants of U.S.-born Mexican American mothers, the findings differed. In the static comparisons, our results show the often-reported similarity in the risk of death of these babies compared to those born to non-Hispanic white mothers. However, when changes over time were modeled, there was an erosion of the relatively favorable survival chances of Mexican American infants. Our models show little change in the relative risk of death for infants of immigrant women. Regarding the other two causes (disorders relating to short gestation and unspecified low birth weight and maternal complications) for which no efficacious innovations occurred, either little change or actual increases in risks were observed. Future studies and health policy efforts should be geared toward further understanding and aggressively working to close infant mortality gaps, especially for infants of U.S.-born black mothers—an effort that will be facilitated by research focused on cause-specific infant mortality.     

The Long-Term Cognitive and Socioeconomic Consequences of Birth Intervals: A Within-Family Sibling Comparison Using Swedish Register Data

We examine the relationship between birth-to-birth intervals and a variety of mid- and long-term cognitive and socioeconomic outcomes, including high school GPA, cognitive ability, educational attainment, earnings, unemployment status, and receiving government welfare support. Using contemporary Swedish population register data and a within-family sibling comparison design, we find that neither the birth interval preceding the index person nor the birth interval following the index person are associated with any substantively meaningful changes in mid- or long-term outcomes. This is true even for individuals born before or after birth-to-birth intervals of less than 12 months. We conclude that in a contemporary high-income welfare state, there appears to be no relationship between unusually short or long birth intervals and adverse long-term outcomes.     

Infant mortality and fertility in three Bavarian villages: An analysis of family histories from the 19th century

Abstract Family history data derived from the records of three parishes in Bavaria provide evidence for several important demographic questions when analysed in conjunction with information concerning the prevalent breast-feeding practices. The results suggest strongly that breast feeding can prolong birth intervals substantially. The evidence concerning the independent influence of infant deaths on subsequent birth intervals is inconclusive. It is clear, however, that even if such an influence did exist it was relatively small, compared to the effect of lactation. In addition the results do not lend support to the hypothesis that couples experiencing low child mortality practised family limitation more than couples experiencing high child mortality. In all three parishes, however, fertility appeared to influence infant mortality. Infants born after short intervals were subject to considerably higher mortality risks than infants following longer intervals.     

The effect of child mortality experience on subsequent fertility: in Pakistan and Bangladesh

Summary This paper presents an empirical analysis of the effects, behavioural and biological, of child mortality experience on subsequent fertility in two South Asian Islamic nations. Data for the investigation came from retrospective pregnancy histories of 2,910 currently married women interviewed in the Pakistan National Impact Survey (1968-69) and from longitudinal vital registration data (1966-2070) of 5,236 women residing in a rural area of Bangladesh collected by the Cholera Research Laboratory. The aim of this study was to assess the importance of the child-replacement motivational response to child death experience after biological effects have been controlled adequately. A common approach employed previously has been to examine cumulative fertility according to child death experience. In Pakistan and Bangladesh, a consistently positive relationship was demonstrated between the number of children ever born and the number of child deaths. This method, however, did not exclude the inverse relationship, the influence of fertility on mortality, nor did it dissect out behavioural from biological effects. Utilizing a measure of subsequent fertility, live-birth-to-live-birth intervals, the study further illustrated another common pitfall. Since the risk of infant death, which leads to shorter birth intervals, is associated with the mother's reproductive history, women with child mortality experience are more likely to experience shorter intervals because of the biological effect of subsequent infant death. Behavioural influences may, therefore, be observed by considering only those birth intervals in which the first-born child survives to the end of the interval. With these limitations controlled, very few, if any, behavioural influences were noted in the Pakistan and Bangladesh data. Median birth intervals in Pakistan varied between 35-43 and 41-42 months, increasing with parity. Within each parity group, no consistent difference was observed between women with and without previous child loss. In Bangladesh, the median birth interval for all women with a surviving infant was 37-2 months. This was shortened to 24-31 months by an infant death. When intervals with infant deaths were excluded, little or no behavioural influence was detected among women of the same parity, but with varying levels of previous child loss. Even without behavioural effects, elimination of infant mortality in Bangladesh would reduce fertility by prolonging the average period of post-partum sterility. In the Bangladesh setting, however, the size of the effect was only about four per cent. This modest effect, more-over, was counterbalanced by an overall increase of net reproduction by seven per cent due to better survivorship of infants.     

The effects of pregnancy spacing on infant and child mortality in Matlab, Bangladesh: how they vary by the type of pregnancy outcome that began the interval

Using high-quality longitudinal data on 125,720 singleton live births in Matlab, Bangladesh, we assessed the effects of duration of intervals between pregnancy outcomes on infant and child mortality and how these effects vary over subperiods of infancy and childhood and by the type of outcome that began the interval. Controlling for other correlates of infant and child mortality, we find that shorter intervals are associated with higher mortality. Interval effects are greater if the interval began with a live birth than with another pregnancy outcome. In the first week of the child's life, the effects of short intervals are greater if the sibling born at the beginning of the interval died; after the first month, the effects are greater if that sibling was still alive. Many relationships found are consistent with the maternal depletion hypothesis, and some with sibling competition. Some appear to be due to correlated risks among births to the same mother.     

Social determinants of low birth weight in a high-risk population

Over ninety low-weight infants were born per thousand live births in South Carolina, based on 96,000 birth records from 1975 and 1979. Higher incidence of low birth weight for black infants cannot be explained away as a result of black/white differences in age or education of mothers, prenatal care, parity or length of birth intervals. Though all these factors are important predictors of birth weight, an increasing propensity to have low-weight babies persists among black mothers even after all these factors are controlled.     

Premature birth and the changing composition of newborn infectious disease mortality: Reconsidering “exogenous” mortality

Linked death and birth records from San Antonio, Texas reveal that infectious infant mortality is increasingly a function of premature birth and low birth weight. Between 1935 and 1944, 4% of infectious infant deaths had associated causes involving prematurity and related conditions; by 1980, 25% of infectious infant deaths involved prematurity and more than 40% of those infants weighed less than 2,500 grams. The shift in birth-weight composition results almost entirely from an increase in very low-weight births. Under conditions of advanced perinatal technology, infectious infant mortality should no longer be viewed as wholly exogenous. These findings further undermine the contemporary relevance of the exogenous-endogenous distinction.     

Birth spacing and child mortality in bangladesh and the Philippines

This analysis uses data from Bangladesh and the Philippines to demonstrate that children who are born within 15 months of a preceding birth are 60 to 80% more likely than other children to die in the first two years of life, once the confounding effects of prematurity are removed. The risks associated with short conception intervals are confined to children who are also high birth order; they persist in the presence of controls for prior familial child mortality, breast-feeding, mother's age, and socioeconomic status. In Bangladesh but not in the Philippines, these effects are confined to the neonatal period.     

Paradox found (again): Infant mortality among the Mexican-origin population in the united states

Recent research suggests that the favorable mortality outcomes for the Mexican immigrant population in the United States may largely be attributable to selective out-migration among Mexican immigrants, resulting in artificially low recorded death rates for the Mexican-origin population. In this paper we calculate detailed age-specific infant mortality rates by maternal race/ethnicity and nativity for two important reasons: (1) it is extremely unlikely that women of Mexican origin would migrate to Mexico with newborn babies, especially if the infants were only afew hours or afew days old; and (2) more than 50% of all infant deaths in the United States occur during the first week of life, when the chances of out-migration are very small. We use concatenated data from the U.S. linked birth and infant death cohort files from 1995 to 2000, which provides us with over 20 million births and more than 150,000 infant deaths to analyze. Our results clearly show that first-hour, first-day, and first-week mortality rates among infants born in the United States to Mexican immigrant women are about 10% lower than those experienced by infants of non-Hispanic, white U.S.-born women. It is extremely unlikely that such favorable rates are artificially caused by the out-migration of Mexican-origin women and infants, as we demonstrate with a simulation exercise. Further, infants born to U.S.-born Mexican American women exhibit rates of mortality that are statistically equal to those of non-Hispanic white women during the first weeks of life and fare considerably better than infants born to non-Hispanic black women, with whom they share similar socioeconomic profiles. These patterns are all consistent with the definition of the epidemiologic paradox as originally proposed by Markides and Coreil (1986).     

Ethnic and Birth Weight Differences in Cause-Specific Infant Mortality

This article examines ethnic differences in cause-specific infant mortality, using linked birth and infant death records from a cohort of New Mexican singleton infants, 1980-1983. The research, which applies log-linear analysis, focuses on the combined influences of ethnicity, birth weight, maternal age, and plurality on birth outcomes--that is, on infant survival and deaths due to perinatal, congenital, and respiratory diseases and to sudden infant death syndrome. The results confirm the pronounced impact of birth weight on infant mortality and identify similarities and differences among Anglo, Hispanic, and American Indian babies with respect to cause-specific infant mortality.     

New evidence about effects of reproductive variables on child mortality in sub-Saharan Africa

There is still considerable uncertainty about how reproductive factors affect child mortality. This study, based on Demographic and Health Survey data from 28 countries in sub-Saharan Africa, shows that mortality is highest for firstborn children with very young mothers. Other children with young mothers, or of high birth order, also experience high mortality. Net of maternal age and birth order, a short preceding birth interval is associated with above average mortality. These patterns change, however, if time-invariant unobserved mother-level characteristics of importance for both mortality and fertility are controlled for in a multilevel–multiprocess model. Most importantly, there are smaller advantages associated with longer birth intervals and being older at first birth. The implications of alternative reproductive ‘strategies’ are discussed, taking into account that if the mother is older at birth, the child will also be born in a later calendar year, when mortality may be lower.     

Rural–Urban Migration and Cross-National Variation in Infant Mortality in Less Developed Countries

The relationship between migration and child health in individual countries is well known, but the cross-national variation in this relationship is largely untested. Using Demographic and Health Survey (DHS) data from 52 medium and low income countries, this study examines the effect of rural–urban migration on infant mortality and whether its effect varies cross-nationally. A secondary objective is to determine whether there is a relationship between the time a child is born in the migration process and infant mortality. Hypotheses are developed on the basis of competing theories on the relationship between migration and health. There are modest, but significant cross-national effects of rural–urban migration on infant mortality, which were better revealed in the presence of family- and child-level variables. The results also show that the unadjusted effects of rural–urban migration are quite substantial, but were largely accounted for by family- and child-level factors including education, socioeconomic status (SES), marital status, birth order, maternal age at child’s birth, and inter-births intervals. The results largely point to a selection process, which is further confirmed by results showing that the hazards of infant death increase with length of urban residence. Programs that target increasing maternal education, improving household SES, and lengthening interbirth intervals would therefore greatly benefit child survival in less developed countries.     

Birth Intervals and Childhood Mortality in Rural Bangladesh

This study investigates the relationship between birth intervals and childhood mortality, using longitudinal data from rural Bangladesh known to be of exceptional accuracy and completeness. Results demonstrate significant but very distinctive effects of the previous and subsequent birth intervals on mortality, with the former concentrated in the neonatal period and the latter during early childhood. The impact of short birth intervals on mortality, however, is substantially less than that found in many previous studies of this issue, particularly for the previous birth interval. The findings are discussed in terms of the potential for family planning programs to contribute to improved child survival in settings such as Bangladesh.     

Demographic Determinants of Infant and Early Child Mortality: A Comparative Analysis

In this paper we examine the relative importance of a number of demographic determinants of infant and early child mortality using information from 39 World Fertility Survey countries. We include sex of the child, age of the mother at the time of the birth, birth order, mother's educational level and a number of indicators of spacing of adjacent births among the correlates of chances of survival for children below the age of five years. Mortality of firstborn children and of those born to teenage mothers is shown to be higher than average; that of later children and those of older mothers was not much higher than average, once other factors are controlled. Effects of poor birth-spacing persist even after other factors have been controlled, and are similar where a sib was born during the two years preceding the birth of the child, regardless of the survival status of that sib; however, mortality was higher when that sib had died, due to increased familial risks of mortality. Rapid subsequent births also raise mortality for their earlier sibs. The findings are generally remarkably consistent in a wide range of countries and associated mortality conditions, although attention is drawn to a few interesting geographically clustered exceptions which deserve further investigation. The study leaves little room for doubt that poor child-spacing is clearly linked to decreased survival chances.     

Parental age and offspring mortality: Negative effects of reproductive ageing may be counterbalanced by secular increases in longevity

As parental ages at birth continue to rise, concerns about the effects of fertility postponement on offspring are increasing. Due to reproductive ageing, advanced parental ages have been associated with negative health outcomes for offspring, including decreased longevity. The literature, however, has neglected to examine the potential benefits of being born at a later date. Secular declines in mortality mean that later birth cohorts are living longer. We analyse mortality over ages 30–74 among 1.9 million Swedish men and women born 1938–60, and use a sibling comparison design that accounts for all time-invariant factors shared by the siblings. When incorporating cohort improvements in mortality, we find that those born to older mothers do not suffer any significant mortality disadvantage, and that those born to older fathers have lower mortality. These findings are likely to be explained by secular declines in mortality counterbalancing the negative effects of reproductive ageing.     

The origins of agriculture: Population growth during a period of declining health

The increase in the Neolithic human population following the development of agriculture has been assumed to result from improvements in health and nutrition. Recent research demonstrates that this assumption is incorrect. With the development of sedentism and the intensification of agriculture, there is an increase in infectious disease and nutritional deficiencies particularly affecting infants and children.Declining health probably increased mortality among infants, children and oldest adults. However, the productive and reproductive core would have been able to respond to this increase in mortality by reducing birth spacing. That is, agricultural populations increased in size, despite higher mortality, because intervals between births became shorter.     

Improving breastfeeding rates in an “at risk” population

A new public health frontier challenging maternity care is addressing the sub-optimal breastfeeding rates of women who are obese. Despite the World Health Organisation's recommendation that breastfeeding is initiated within the first hour of birth and continued exclusively for six months, less than half of infants and young children globally are optimally breastfed. While initiation rates of exclusive breastfeeding immediately after birth are as high as 90 percent in Australia, this rate dramatically declines in the first few weeks postpartum, with only approximately 15 percent of infants exclusively breastfed to five months of age (less than 6 months). The aim of this paper was to highlight difficulties obese women have breastfeeding and highlight implications for research and practice.