Pediatric paradox: heterogeneity in the birth cohort

Comparisons of birth-weight-specific infant mortality indicate that low-birth-weight African American infants have lower mortality than low-birth-weight European American infants despite higher infant mortality overall-the "pediatric paradox." One explanation is heterogeneity in birth weight. Analyses of African American and European American births suggest that birth cohorts consist of two heterogeneous subpopulations. One appears to account for normal births, whereas the other may consist of compromised births. Estimates of infant mortality indicate that the compromised subpopulation has higher overall mortality but lower birth-weight-specific mortality. We attribute lower birth-weight-specific infant mortality in the compromised subpopulation to higher rates of fetal loss. Compared to European American birth cohorts, African American birth cohorts have (1) higher birth-weight-specific mortality in the normal subpopulation, (2) larger compromised subpopulations, and (3) lower birth-weight-specific mortality in the compromised subpopulation. Consequently, the pediatric paradox is attributable to greater rates of compromised pregnancies and higher fetal losses among African Americans.     

Increasing pre-term and low-birth-weight rates over time and their impact on infant mortality in south-east Brazil

This study investigates the possible effects of pre-term births and low birth weight on infant mortality rates (IMRs) over a 15-year period in Ribeir?o Preto, Brazil, based on surveys carried out in 1978/79 and 1994. The 1978/79 survey included 6750 births over a 12-month period and the 1994 survey 2846 births over a 4-month period. Infant deaths were retrieved monthly from the city register. Infant mortality rate decreased from 36.6 to 16.9 deaths per 1000 over 15 years. The decrease in IMR was larger in the 2500-2999 g group than in any other group. The observed falls in IMR were attributable to decreases in birth-weight-specific mortality rates. Likewise, there was a general decrease in IMR in mild, moderate and severe pre-term births. The incidence rate ratio of infant mortality between surveys was 0.46 (95% CI 0.34-0.63); it increased to 0.57 (95% CI 0.35-0.75) when adjusted for birth weight and other factors in the model and rose to 0.69 (95% CI 0.49-0.97) when adjusted for length of gestation and other variables. The increase in pre-term births and low birth weight may have had, at most, a marginal effect on the IMR. Progress in the care of newborns may have decreased the mortality risk, but even mild pre-term birth still has an impact on infant mortality. There is room for further improvement in IMR by tackling the high rates of pre-term birth.     

Modeling the pediatric paradox: Birth weight by gestational age

Abstract

The “pediatric paradox” of African versus European American infant mortality is often observed with respect to birth weight, but rarely to gestational age, even though the two measures are biologically related. This paper models the pediatric paradox by birth weight and gestational age simultaneously, using Covariate Density Defined mixture of logistic regressions (CDDmlr) fitted to 1985–1988 New York State births. The model controls for unobserved heterogeneity and isolates the pediatric paradox in the “compromised” subpopulation. The paradox is not limited to low birth weights and/or short gestational ages, but surrounds the normal birth range. Nevertheless, the pediatric paradox is only observed in the marginal distribution of birth weight and not the marginal distribution of gestational age. These results are consistent with the hypothesis that higher fetal losses in the “compromised” subpopulation may be responsible for the pediatric paradox and that African versus European American infant mortality differentials are underestimated.     

THE OBSTETRICIAN'S RESPONSIBILITY IN INFANT MORTALITY

Although infant mortality has been remarkably reduced, stillbirth and neonatal death rates have been improved very little. Efforts at lowering the fetal death rate must be directed to those conditions affecting the fetus during labor or immediately afterward.Prevention of premature labor and better care of the premature infant during labor and the neonatal period offer hope of a greater salvage of premature infants. Proper environment and trained personnel are necessary.Spontaneous delivery is safest for the infant. Difficult operative procedures are associated with a high incidence of birth trauma, asphyxia and death.Since asphyxia is one of the chief causes of infant death, prevention, diagnosis and treatment of it are most important. Administration of oxygen to mildly asphyxiated infants before the injury has become irreversible may help to prevent late manifestations of anopia.     

Quantifying the Search Behaviour of Different Demographics Using Google Correlate

Vast records of our everyday interests and concerns are being generated by our frequent interactions with the Internet. Here, we investigate how the searches of Google users vary across U.S. states with different birth rates and infant mortality rates. We find that users in states with higher birth rates search for more information about pregnancy, while those in states with lower birth rates search for more information about cats. Similarly, we find that users in states with higher infant mortality rates search for more information about credit, loans and diseases. Our results provide evidence that Internet search data could offer new insight into the concerns of different demographics.     

Rates of trisomies 21, 18, 13 and other chromosome abnormalities in about 20 000 prenatal studies compared with estimated rates in live births

Summary Data were analyzed on the results of 19675 prenatal cytogenetic diagnoses reported to two chromosome registries on women aged 35 or over for whom there was no known cytogenetic risk for a chromosome abnormality except parental age. The expected rates at amniocentesis of 47,+21; 47,+18; 47,+13; XXX; XXY; XYY; and other clinically significant cytogenetic defects by maternal age were obtained from a regression analysis on the observed rates, using a first degree exponential model. After an adjustment for maternal age, these rates were compared with previously estimated rates by maternal age in live births. The rates of 47,+21 at amniocentesis and live birth are approximately parallel, with the latter about 80% of the amniocentesis rates. The rates of 47,+18 at amniocentesis and live birth are approximately parallel, with the live birth rates about 30% of the amniocentesis rates, consistent with high fetal mortality of 47,+18 after amniocentesis. The rates of 47,+13 at amniocentesis indicate an increase in maternal age that is not as marked as thar previously estimated in live births. The rates at amniocentesis for XXX and XXY increase with maternal age, with the rates of XXY almost identical to those estimated previously in live births, suggesting no late fetal mortality of XXY. The rates of XYY show a slight decrease with maternal age also consistent with little late fetal mortality of XYY. No consistent trend with age is seen for the pooled group of other clinically significant defects.     

Extrinsic Mortality Effects on Reproductive Strategies in a Caribbean Community

Extrinsic mortality is a key influence on organisms’ life history strategies, especially on age at maturity. This historical longitudinal study of 125 women in rural Domenica examines effects of extrinsic mortality on human age at maturity and pace of reproduction. Extrinsic mortality is indicated by local population infant mortality rates during infancy and at maturity between the years 1925 and 2000. Extrinsic mortality shows effects on age at first birth and pace of reproduction among these women. Parish death records show huge historical variation in age-specific mortality rates. The infant mortality rate (IMR) in the early 1920s was low, increased dramatically beginning in 1929, and reached a maximum in the 1950s, at which point IMR declined steadily to its present low rate. The mortality rate early in life showed a quadratic association with age at first birth. Women who experienced conditions of low IMR early in life reproduced relatively late in life. Those born into moderately high levels of infant mortality tended to reproduce earlier than those born at low levels. At very high infant mortality levels early in life, women went on to delay reproduction until relatively late, possibly as a result of somatic depletion and energetic stress associated with the conditions that lead to high IMR. Population mortality rates at age of maturity also showed a quadratic association with age at first birth. The pace of reproduction, estimated as number of surviving offspring controlled for maternal age, showed a similar quadratic effect. There were complex interactions between population mortality rates in infancy and at maturity. When extrinsic mortality was high during infancy, extrinsic mortality later in life had little effect on timing of first birth. When extrinsic mortality was low to moderate in infancy, extrinsic mortality later in life had significant effects on adult reproduction. I speculate that these effects are mediated through development of personality facets associated with reproduction.     

Case fatality among infants with congenital malformations by lethality

OBJECTIVE: Infant mortality rates continue to show that congenital anomalies are the leading cause of infant death in the United States. However, studies of factors contributing to increased mortality across different types of congenital anomalies have been limited. The objective of this study was to assess whether the likelihood of infant mortality varied by maternal race and ethnic group while considering the severity of the birth defect. METHODS: A retrospective cohort analysis was conducted using data from Colorado's statewide, population-based birth defects surveillance system (CRCSN). The cohort included infants, born between 1995 and 2000 to Colorado resident mothers, who were diagnosed with major congenital malformations stratified by degree of lethality. Multiple logistic regression was performed for each level of lethality, and included the following potential explanatory variables: maternal race/ethnicity, clinical gestation, birth weight, maternal education level, maternal age, and sex of child. RESULTS: Within the low/very low lethality cohort, maternal race/ethnicity of Black/non-Hispanic was associated with increased risk of infant mortality, OR 2.81 (1.41-5.19), as were low and very low birth weight, OR 2.21 (1.12-4.04) and 19.31 (11.84-31.01), respectively. Maternal race/ethnicity was not a significant risk factor in either high or very high lethality groups; however, the interaction between birth weight and gestational age significantly increased the risk of mortality. CONCLUSIONS: Through the use of statewide, population-based birth defects surveillance data, a disparity in infant mortality has been identified in a specific subset of the population that could be investigated further and targeted for prevention activities.     

Infant mortality in Zambia: socioeconomic and demographic correlates

Trends in infant mortality in Zambia suggest a reversal of the decline experienced between the 1960s and the late 1970s. From a high of about 140, infant mortality rate declined to about 90 in the late 1970s only to rise again to 100 by 1996. Data on 5,600 births born between 1987 and 1992, and 6,630 births between 1991 and 1996 from the Zambian DHS are analyzed to identify socioeconomic and demographic correlates of infant mortality. Demographic factors such as small size at birth and short birth intervals are associated with higher neonatal mortality. In the post-neonatal period, urban children from poorer households had the highest mortality between 1991-1996. Also, differences in infant mortality rates between provinces narrowed. Children born in the most developed province of Lusaka had as high of risk of dying as those from Luapula, a province with a history of extremely high mortality rates in Zambia.     

Disparities and Trends in Birth Outcomes,Perinatal and Infant Mortality in Aboriginal vs. Non-Aboriginal Populations: A Population-Based Study in Quebec,Canada 1996–2010

Background

Aboriginal populations are at substantially higher risks of adverse birth outcomes, perinatal and infant mortality than their non-Aboriginal counterparts even in developed countries including Australia, U.S. and Canada. There is a lack of data on recent trends in Canada.

Methods

We conducted a population-based retrospective cohort study (n = 254,410) using the linked vital events registry databases for singleton births in Quebec 1996–2010. Aboriginal (First Nations, Inuit) births were identified by mother tongue, place of residence and Indian Registration System membership. Outcomes included preterm birth, small-for-gestational-age, large-for-gestational-age, low birth weight, high birth weight, stillbirth, neonatal death, postneonatal death, perinatal death and infant death.

Results

Perinatal and infant mortality rates were 1.47 and 1.80 times higher in First Nations (10.1 and 7.3 per 1000, respectively), and 2.37 and 4.46 times higher in Inuit (16.3 and 18.1 per 1000, respectively) relative to non-Aboriginal (6.9 and 4.1 per 1000, respectively) births (all p<0.001). Compared to non-Aboriginal births, preterm birth rates were persistently (1.7–1.8 times) higher in Inuit, large-for-gestational-age birth rates were persistently (2.7–3.0 times) higher in First Nations births over the study period. Between 1996–2000 and 2006–2010, as compared to non-Aboriginal infants, the relative risk disparities increased for infant mortality (from 4.10 to 5.19 times) in Inuit, and for postneonatal mortality in Inuit (from 6.97 to 12.33 times) or First Nations (from 3.76 to 4.25 times) infants. Adjusting for maternal characteristics (age, marital status, parity, education and rural vs. urban residence) attenuated the risk differences, but significantly elevated risks remained in both Inuit and First Nations births for the risks of perinatal mortality (1.70 and 1.28 times, respectively), infant mortality (3.66 and 1.47 times, respectively) and postneonatal mortality (6.01 and 2.28 times, respectively) in Inuit and First Nations infants (all p<0.001).

Conclusions

Aboriginal vs. non-Aboriginal disparities in adverse birth outcomes, perinatal and infant mortality are persistent or worsening over the recent decade in Quebec, strongly suggesting the needs for interventions to improve perinatal and infant health in Aboriginal populations, and for monitoring the trends in other regions in Canada.     

Risk factors for perinatal mortality in Canada

A population-based computer record-linkage study of infant births and deaths in 1978 and 1979 in eight Canadian provinces (Quebec and Newfoundland were excluded) was undertaken to permit analysis of perinatal mortality in relation to maternal and infant characteristics. Perinatal mortality rates were significantly higher in nonurban than in urban areas (p < 0.05). A logistic regression model was used to assess the effects on perinatal mortality of variables reported on birth and stillbirth records. This model included length of gestation, infant''s birth weight and sex, number of previous births and number of previous stillbirths as well as an interaction term for length of gestation and birth weight. For early-neonatal mortality, odds ratios over 8 were observed for birth weight less than 2500 g or gestation less than 35 weeks. About 75% of early-neonatal mortality was attributable to low birth weight or fetal immaturity. Greater emphasis should be placed on the prevention of low birth weight.     

Referral of mothers and infants for intensive care.

During 1975-7, 96 mothers were referred to University College Hospital for delivery from 39 other hospitals because their pregnancies were considered to be at very high risk. One hundred of the 111 infants born to the 96 mothers weighed 2500 g or less and 60 weighed 1500 g or less. A high proportion of the infants developed serious illnesses necessitating intensive care. The birth-weight-specific neonatal mortality rates of the infants were much lower than those of infants born in England and Wales as a whole and were also lower than those of the 370 infants transported to this hospital for intensive care after delivery elsewhere. Whenever possible mothers with very high-risk pregnancies should be referred for delivery to centres with full facilities for the intensive care of the mother, fetus, and newborn infant.     

The Apgar Score and Infant Mortality

Objective

To evaluate if the Apgar score remains pertinent in contemporary practice after more than 50 years of wide use, and to assess the value of the Apgar score in predicting infant survival, expanding from the neonatal to the post-neonatal period.

Methods

The U.S. linked live birth and infant death dataset was used, which included 25,168,052 singleton births and 768,305 twin births. The outcome of interest was infant death within 1 year after birth. Cox proportional hazard-model was used to estimate risk ratio of infant mortality with different Apgar scores.

Results

Among births with a very low Apgar score at five minutes (1–3), the neonatal and post-neonatal mortality rates remained high until term (≥ 37 weeks). On the other hand, among births with a high Apgar score (≥7), neonatal and post-neonatal mortality rate decreased progressively with gestational age. Non-Hispanic White had a consistently higher neonatal mortality than non-Hispanic Black in both preterm and term births. However, for post-neonatal mortality, Black had significantly higher rate than White. The pattern of changes in neonatal and post-neonatal mortality by Apgar score in twin births is essentially the same as that in singleton births.

Conclusions

The Apgar score system has continuing value for predicting neonatal and post-neonatal adverse outcomes in term as well as preterm infants, and is applicable to twins and in various race/ethnic groups.     

Stochastic variation in sex ratios in infant mortality rates due to small samples in provisioned Japanese macaque (<Emphasis Type="Italic">Macaca fuscata</Emphasis>) populations

Sex differences in infant mortality in provisioned Japanese macaque populations were examined using 10 data sets from five populations. The results indicate that there was no available data set in which a sex difference in infant mortality was statistically significant. To examine whether the observed sex ratios in infant mortality rates could be the product of stochastic variation in small samples, a correlation between sample size and the magnitude of sex ratios in infant mortality rates was also examined. Notably, the magnitude of sex ratios in infant mortality rates declined significantly as sample sizes increased. These results suggest that previously reported marked sex ratios in infant mortality could be the product of stochastic variation in small samples.     

Infant and child mortality in Bangladesh

Socioeconomic differences and trends in infant and child mortality in Bangladesh are examined using data from the 1975 World Fertility Survey and 1979 Contraceptive Prevalence Survery. There is evidence of some recent decline in infant mortality and child mortality. Logit analysis of infant and child mortality indicates that sociodemographic variables such as mother's education, recent period, or higher birth orders, has significant independent effects upon the reduction of infant and child mortality. Other variables such as fetal loss, father's education, or land ownership had no consistent significant effect. On the other hand the effect of urban residence on infant and child mortality was positive after the control of sociodemographic variables. Mere concentration on the supply of modern medical services may bring limited returns unless they are reinforced by appropriate social changes, in particular those affecting the socioeconomic status of women. Educated mothers are likely to belong to higher income households, have better knowledge of how to care for children, and can bring more resources to the care of a sick child.     

Determinants of infant and child mortality in the West Bank and Gaza Strip

Infant and child mortality in the West Bank and Gaza Strip has steadily reduced since 1967, even though fertility has remained extremely high. In this paper the determinants of infant and child mortality are discussed, with particular emphasis on the role of consanguineous marriages, short birth spacing and maternal education. It is shown that short birth spacings and type of marriage are more important determinants of infant mortality than maternal education. Moreover, the relative role of consanguineous marriages appears to increase with time.     

Infant and child mortality in Pakistan--some trends and differentials

Data from reproductive histories collected in the Population, Labor Force and Migration Survey (PLM) of 1979 are used to analyze trends and differentials in infant and child mortality in Pakistan. Comparisons with the Pakistan Fertility Survey (PFS) findings are also presented. The main concern is to provide from the latest national data, the PLM, direct measures of infant and child mortality and to demonstrate the relatively static and low chances of survival for children in Pakistan. The apparent trends from the PLM and the PFS are similar and seem to confirm that infant and childhood mortality has ceased to decline, at least rapidly, since 1965-69. Neonatal mortality is higher at levels of 70-85 deaths/1000 compared to postneonatal mortality of 40-60 deaths/1000. Improvements in neonatal rates from 1950 until 1975 are only approximately 1/2 of those for postneonatal rates for that period. The relationship between maternal age and mortality in the PLM data confirms that children of youngest mothers experienced the highest rates of infant mortality; mortality is again higher for children of oldest mothers aged 35 and above. The pattern of mortality in the 2 surveys is similar except that in the PFS there was little variation among births higher than 5th order. Sex differentials in mortality are very clear in both surveys. Boys have higher chances of dying in the 1st month of life but then the probability of their surviving from age 1 to 5 years is higher, reflecting the behavioral preference for the male sex in this society. The data also demonstrate an almost monotonic decline in infant and child mortality associated with longer birth intervals. Childhood mortality shows a less clear association with preceding birth interval than does infant mortality. While neonatal mortality is much higher in rural than in urban areas, there are negligible differences in the postneonatal rate. The urban-rural differential continues into childhood, reflecting lower health care and nutrition of children in rural areas. The data confirm the importance of parental education, particularly that of mothers, as a contributor to the health and mortality of infants. Mortality between age 1 and 5 years for children of the rural educated group is lower than that for the urban uneducated indicating the strong influence that education of mothers can have in preventing child loss. The combined evidence from the PFS and PLM data stresses the importance of improving health facilities in the rural areas, in aneffort to reduce the differences in mortality by area of residence. The data from both surveys also suggest the need to restrict motherhood to between the ages of 20 and 34, when obstetrical and health risks are minimal, and indicate the definite advantages of increasing the spacing between children.     

The influence of birth timing upon infant growth and survival in Captive Rhesus Macaques (Macaca mulatto)

Weights, growth rates, and mortality data of 815 captive-born Macaca mulattainfants were studied to determine if date of birth influences infant growth and survival. The six groups studied displayed a unimodal spring-summer birth season that has become systematically more restricted since 1977. Males exhibited higher rates of stillbirth and neonatal death and were more frequently born outside the normal birth season, when infant mortality was more common. Within the normal birth season, infant weight increased linearly with birth date, and infant growth rate declined linearly with birth date. Female infants with weights and growth rates near the developmental norm, especially those born in the middle of the birth season, have the greatest probability of survival. Males are more likely to survive if their weights and growth rates exceed the developmental norm, and thus male infants might be initially more costly to produce than female infants. These results are inconsistent with the hypothesis that offspring of high-ranking males, which conceived predominantly in the first third of the breeding season, enjoy a selective advantage.     

Factors affecting infant and child mortality

This paper examines the determinants of infant and child mortality variations in Jordan, Yemen, Egypt, and Tunisia using data from WFS surveys. The analysis considers biological correlates of mortality--mother's age, birth order, birth interval, and previous infant loss--and several social factors--mother's and father's education, mother's residence, father's occupation, and mother's work experience since marriage. The estimates for the 4 countries show large variations in the mortality rates and an expected pattern of declining infant and child mortality during the period of 20 years prior to the survey. Further, the proportionate decline in child mortality in each country was generally greater than the proportionate decline in infant mortality. A persistent pattern of higher child mortality for females than for males is found, suggesting preferential care and treatment of male offspring. The higher mortality risk is found for infants born to very young and very old mothers, with short previous birth intervals, of higher birth orders, and where the previous infant had died. Among the socioeconomic characteristics, the education of the mother and rural-urban residence are found to affect infant survival. In childhood, among the demographic factors, only birth interval shows a significant effect on mortality. The risk of child mortality decreases considerably with the increase in the birth interval. The analysis of the effect of breastfeeding on mortality, although based on limited information, clearly shows the beneficial effect of breastfeeding on the infant's survival, especially during the early months of life. For all countries, the mortality rate for the non-breastfeeders is substantially higher than for the breastfeeders even when the effect of the other covariates is controlled.     

Demographic and health patterns in a rural community from the Basque area in Spain (1800-1990)

In this work, the evolution of demographic and health patterns in a Basque rural population from Spain is analysed, as they relate to progress in demographic and epidemiological transition. For this purpose, parochial record data on 13,298 births and 9,215 deaths, registered during the 19th and 20th centuries (1800-1990), were examined. The study area is a rural community called Lanciego, which is located at the southern end of the Rioja Alavesa area (Alava Province, Basque Country). In Lanciego, demographic transition began in the final decade of the 19th century, when a definite, irreversible trend began towards a reduction in mortality. The decrease in the birth rate came later than that in the death rate, and did not start until the 1930s. The post-transitional stage seemed to be reached in the 1970s, when the birth and death rates showed values below 20 per 1,000. Other characteristics observed for the post-transitional stage in Lanciego are: (i) very low rates of infant mortality achieved at the expense of effective control of exogenous mortality; (ii) the mortality curve by ages changes from a U-shape (typical of populations with a high infant mortality rate and low life expectancy at birth) to a J-shape more characteristic of modern societies where longevity and life expectancy are considerably higher; (iii) a certain level of over-mortality among women in the senior age group (>65); and (iv) a significant proportion of mortality in recent times (1970-90) resulting from cardiovascular diseases and malignant neoplasms (post-transition causes). This last point is in contrast with observations from the first four decades of the 20th century, when infectious diseases and respiratory ailments were determining factors in mortality among this population. The data provided by the study of the variation over time in demographic and health patterns indicate that reducing the risk of mortality is one of the most important preconditions for fertility decline.