Infant mortality: comparison between two birth cohorts from Southeast and Northeast, Brazil

OBJECTIVE: To obtain population estimates and profile risk factors for infant mortality in two birth cohorts and compare them among cities of different regions in Brazil. METHODS: In Ribeir?o Preto, southeast Brazil, infant mortality was determined in a third of hospital live births (2,846 singleton deliveries) in 1994. In S?o Luís, northeast Brazil, data were obtained using systematic sampling of births stratified by maternity unit (2,443 singleton deliveries) in 1997-1998. Mothers answered standardized questionnaires shortly after delivery and information on infant deaths was retrieved from hospitals, registries and the States Health Secretarys' Office. The relative risk (RR) was estimated by Poisson regression. RESULTS: In S?o Luís, the infant mortality rate was 26.6/1,000 live births, the neonatal mortality rate was 18.4/1,000 and the post-neonatal mortality rate was 8.2/1,000, all higher than those observed in Ribeir?o Preto (16.9, 10.9 and 6.0 per 1,000, respectively). Adjusted analysis revealed that previous stillbirths (RR=3.67 vs 4.13) and maternal age <18 years (RR=2.62 vs 2.59) were risk factors for infant mortality in the two cities. Inadequate prenatal care (RR=2.00) and male sex (RR=1.79) were risk factors in S?o Luís only, and a dwelling with 5 or more residents was a protective factor (RR=0.53). In Ribeir?o Preto, maternal smoking was associated with infant mortality (RR=2.64). CONCLUSIONS: In addition to socioeconomic inequalities, differences in access to and quality of medical care between cities had an impact on infant mortality rates.     

Widening ethnic disparities in infant mortality in southern Brazil: comparison of 3 birth cohorts

Objectives. We analyzed trends in mortality among infants born to White and to Black or mixed-race women in 3 population-based cohorts representing all births in 1982, 1993, and 2004 in Pelotas, southern Brazil.Methods. Births were assessed during daily visits to all maternity hospitals. Maternal skin color was classified by the interviewers as White or Black or multi-racial. We used logistic regression to adjust for socioeconomic, demographic, and health services variables.Results. The mortality rate among infants born to White mothers declined from 30.4 per 1000 live births in 1982 to 13.9 per 1000 in 2004, compared with 53.8 per 1000 to 30.4 per 1000 among those born to Black and mixed-race mothers. Differences for neonatal mortality were even more marked, with reductions of 47% and 11% for infants born to White and Black or mixed-race women, respectively. Adjusted analyses showed that ethnic group differences in neonatal and infant mortality were partly explained by differences in poverty and prenatal care.Conclusions. Over a 22-year period, improvements in health indicators were greater for infants born to White women than for other infants. The widening racial gap requires special attention from policymakers.Infant mortality, an often-used indicator of population health and well-being, received less public interest in the 1990s than in previous decades,1 because the appearance of HIV/ AIDS and the growing recognition of malaria pushed it off the political agenda.2 Over the last several years, however, the global community has given greater attention to mortality among young children. Reduction of infant and child mortality is 1 of 8 United Nations Millennium Development Goals to dramatically reduce world poverty by 2015. The fourth Millennium Development Goal focuses directly on child survival, and infant mortality rate is one of the indicators used to monitor progress toward this goal.3Socioeconomic disparities, as well as race and gender inequities, have been linked to health outcomes and access to and use of health care services.4 In developed countries, although absolute infant mortality has fallen dramatically, huge disparities still persist among selected populations.5 Ethnic disparities in infant mortality, which are well documented in many countries, have remained unchanged or have even increased over the past decades.6^–8Infant mortality in Brazil has improved substantially, from 112 deaths per 1000 live births in 1960 to an estimated 25 deaths per 1000 live births in 2002.9 Major changes in health systems occurred during these 2 decades, of which the most important was the creation of the Unified Health System (Sistema Único de Saúde) by the 1988 Brazilian Constitution. Access to maternal and child care was defined as a universal right in the constitution, and government health insurance became universal in 1989. Inequities in child health have been documented, however, and wide social differences still persist.10^,11 Many health disadvantages, such as high prevalence of low birth-weight and preterm births, poor nutritional status, and increased risk of death during the first year of life, have been found to be more prevalent among Black infants than among White ones.12^,13The city of Pelotas in southern Brazil, although located in a relatively developed area of the country, has a highly inequitable income distribution. Infant mortality has remained almost stable over the last several years. During the years 1982, 1993, and 2004, birth cohort studies representing all births in the city were carried out, providing a unique opportunity for assessing ethnic group inequalities. We analyzed time trends in infant mortality between children born to White women and those born to Black or mixed-race women. We add a temporal dimension to existing analyses and explore pathways that may account for the ethnic differences in infant mortality in a middle-income setting.     

Risk factors for the increasing caesarean section rate in Southeast Brazil: a comparison of two birth cohorts, 1978-1979 and 1994.

BACKGROUND: Brazil has the highest caesarean section (CS) rate in the world (36.4% in 1996). METHODS: Risk factors for increasing CS rate were studied in two population-based cohorts of singleton live births in families residing in the municipality of Ribeirao Preto, State of Sa? Paulo, Southeast Brazil. The first comprised births from June 1978 to May 1979 (6750 births-one-year survey) and the second births from May to August 1994 (2846 births-4-month survey). Multiple unconditional logistic regression modelling was used to control for confounding. RESULTS: The CS rate rose from 30.3% in 1978-1979 to 50.8% in 1994. In 1978-1979, socioeconomic, reproductive and demographic variables, and health service factors were associated with CS rate. In 1994, only reproductive, demographic and health service factors remained associated, e.g. hour of delivery (from 7 a.m. to 12 p.m.), attendance by the same physician for prenatal care and delivery, > or =4 prenatal visits, maternal age > or =30 years, 1-3 previous live births and birthweight 3500-3999 g. CONCLUSION: Caesarean section in Brazil is widely performed for non-medical reasons in which physician convenience plays an important role. There is an urgent need for public health interventions to reduce the CS rate in Brazil, mainly directed towards cultural beliefs and physician behaviour.     

Trends in low birth weight: a comparison of two birth cohorts separated by a 15-year interval in Ribeir?o Preto,Brazil.

The incidence and some determinants of low birth weight (LBW) were studied in two population-based cohorts of singletons born live to families in Ribeirão Preto, São Paulo State, Brazil. The first cohort comprised infants born between June 1978 and May 1979 (6750 births--population survey) and the second, infants born between May and August 1994 (2990 births--sample survey). The incidence of LBW was 7.2% in 1978-79 and 10.6% in 1994. After adjustment for confounding factors, the following determinants remained significant in 1978-79: female sex, maternal age > or = 35 years, preterm delivery, < four antenatal health visits, maternal smoking, lower level of maternal education, and manual work/unemployment. In 1994, the significant determinants were preterm delivery, maternal smoking and caesarean section. The adjusted percentage population attributable risk (PAR%) fell for the majority of risk factors but increased for caesarean section, preterm birth, multiparity (> or = 5), primiparity and non-cohabitation. The increase in the rate of LBW from 1978-79 to 1994 was higher for families with more qualified occupations, and occurred only for infants delivered at 36-40 weeks'' gestational age and weighing 1500-2499 g, i.e. those most likely to be born by elective caesarean section. The caesarean section rate rose from 30.3% in 1978-79 to 51.1% in 1994. The increase in LBW was probably due to iatrogenic practices associated with elective caesarean section.     

Infant mortality in three population-based cohorts in Southern Brazil: trends and differentials

We studied time trends in infant mortality and associated factors between three cohort studies carried out in Pelotas, Rio Grande do Sul State, Brazil, in 1982, 1993, and 2004. All hospital births and deaths were determined by means of regular visits to hospitals, registrar's offices, and cemeteries. This data was used to calculate neonatal, post-neonatal, and infant mortality rates per thousand live births. Rates were also calculated according to cause of death, sex, birth weight, gestational age, and family income. The infant mortality rate fell from 36.4 per 1,000 live births in 1982 to 21.1 in 1993 and 19.4 in 2004. Major causes of infant mortality in 2004 were perinatal causes and respiratory infections. Mortality among low birth weight children from poor families fell 16% between 1993 and 2004; however, this rate increased by more than 100% among high-income families due to the increase in the number of preterm deliveries in this group. The stabilization of infant mortality in the last decade is likely to be due to excess medical interventions relating to pregnancies and delivery care.     

Factors associated with preterm births in southeast Brazil: a comparison of two birth cohorts born 15 years apart

An increase in preterm deliveries in Ribeirão Preto stimulated an analysis of possible explanatory factors. Two cohorts of singleton livebirths were studied, the first based on 6746 births in 1978–9 and the second based on 2846 births in 1994. A logistic regression was carried out to assess the association of preterm birth with several socio‐demographic, behavioural and clinical variables, including year of survey. Delivery in private settings compared with a public setting, maternal age of 17 compared with any other age group, and mothers who had had previous abortions and previous stillbirths were associated with greater rates of preterm birth. Although there was an increase in preterm birth rates regardless of mode of delivery, the increase was greater in the caesarean section group than in the vaginal delivery group. Over the study period, deliveries in private hospitals and caesarean section operations increased markedly (from 4% to 36% and from 30% to 51% respectively). Caesarean section may be the main contributor to the increase of preterm birth rate in this study. It is essential to ensure that health‐care staff, especially those in private facilities, are properly educated and audited.     

Maternal nutrition and duration of breastfeeding in a birth cohort in Pelotas, Brazil

OBJECTIVE: The effects of maternal nutritional status on the duration of breastfeeding are inconsistent in the literature. A population-based cohort study was set to investigate this relationship. METHODS: Nine hundred and seventy seven mothers giving birth in 1993 (20% of that year's births) were studied. Studied maternal characteristics included nutritional status, social, economic, and demographic variables. The effects of these variables on the prevalence of breastfeeding at six months were analyzed through logistic regression. Cox regression was applied to analyze the effects on the duration of breastfeeding. RESULTS: Multivariate logistic regression analysis showed a higher prevalence of breastfeeding among women with a pre-pregnancy weight of 49 kg or more (odds ratio = 1.31; CI(95%) 1.04 - 1.64). The association with maternal height was not significant (p=0.06). Cox regression also showed a non-significant protective effect of having a higher pre-pregnancy weight (hazard ratio = 0.91; CI(95%) 0.82 - 1.01). The duration of breastfeeding duration was not associated with maternal height. Weight gain during pregnancy was not associated with breastfeeding in either analyses. Other variables associated with the duration of breastfeeding in both analyses were maternal age, parity, smoking, and gestational age. Family income was associated with the prevalence of breastfeeding at six months, and birthweight was associated with the duration of breastfeeding. CONCLUSIONS: Pre-pregnancy nutritional status is a stronger predictor of breastfeeding than weight gain during pregnancy.     

Maternal-child health in Pelotas, Rio Grande do Sul State, Brazil: major conclusions from comparisons of the 1982, 1993, and 2004 birth cohorts

Important changes were observed in maternal characteristics, health care indicators, and child health during the 22 years covered by the three population-based birth cohort studies conducted in the city of Pelotas, Southern Brazil. Maternal education levels improved, cigarette smoking during pregnancy was reduced, and birth intervals became longer. Also, there were more single mothers, and maternal obesity increased. Coverage of antenatal and delivery care by professionals improved, but inductions and caesarean sections increased markedly, the latter accounting for 45% of deliveries in 2004. With regard to child health, the reductions in neonatal and infant mortality rates were modest, and the significant increase in preterm births--14.7% of all births in 2004--appears to have colluded with this stagnation. Other infant health indicators, such as immunization coverage and breastfeeding duration, showed improvements over the period. Regarding infant nutrition, malnourishment at age 12 months decreased, but the prevalence of overweight was higher in 2004. The existence of three population-based birth cohorts using comparable methodology allowed for the study of important secular trends in maternal and child health.     

Infant mortality and low birth weight in cities of Northeastern and Southeastern Brazil

OBJECTIVE: To compare estimates of low birth weight (LBW), preterm birth, small for gestational age (SGA), and infant mortality in two birth cohorts in Brazil. METHODS: The two cohorts were performed during the 1990s, in S o Lu s, located in a less developed area in Northeastern Brazil, and Ribeir o Preto, situated in a more developed region in Southeastern Brazil. Data from one-third of all live births in Ribeir o Preto in 1994 were collected (2,839 single deliveries). In S o Lu s, systematic sampling of deliveries stratified by maternity hospital was performed from 1997 to 1998 (2,439 single deliveries). The chi-squared (for categories and trends) and Student t tests were used in the statistical analyses. RESULTS: The LBW rate was lower in S o Lu s, thus presenting an epidemiological paradox. The preterm birth rates were similar, although expected to be higher in Ribeir o Preto because of the direct relationship between preterm birth and LBW. Dissociation between LBW and infant mortality was observed, since S o Lu s showed a lower LBW rate and higher infant mortality, while the opposite occurred in Ribeir o Preto. CONCLUSIONS: Higher prevalence of maternal smoking and better access to and quality of perinatal care, thereby leading to earlier medical interventions (cesarean section and induced preterm births) that resulted in more low weight live births than stillbirths in Ribeir o Preto, may explain these paradoxes. The ecological dissociation observed between LBW and infant mortality indicates that the LBW rate should no longer be systematically considered as an indicator of social development.     

Hospital admissions from birth to early adolescence and early-life risk factors: the 11-year follow-up of the 1993 Pelotas (Brazil) birth cohort study

The aim of this prospective analysis was to describe the cumulative incidence of hospital admissions in the first year of life and between 1 and 11 years of age and to explore associated factors. Hospital admissions were collected through regular monitoring in the first year of life, and through maternal report on admissions between 1 and 11 years. Analyses were stratified by sex and adjusted for confounding factors. 18.1% of children were hospitalized in the first year of life, and 30.7% between ages 1 and 11 years. Among boys, hospital admission in the first year was associated with low family income, paternal smoking during pregnancy, preterm delivery, and low birthweight. Among girls, in addition to the variables described for boys, black/mixed skin color was also a risk factor for hospital admission. For admissions between 1 and 11 years of age, low family income and gestational age > 37 weeks were found to be significant risk factors.     

Causes of perinatal mortality in Pelotas, RS (Brazil). Use of a simplified classification

The causes of perinatal mortality among 7392 hospital births which occurred in Pelotas, RS, Brazil during 1982, were analyzed using the simplified classification described by Wigglesworth. The main advantage of this classification is that it can be used even in places where postmortems are seldom performed. The perinatal deaths were classified into 5 groups: a) macerated fetuses without malformations; b) congenital malformations; c) immaturity; d) asphyxia, and e) other causes of death. The perinatal mortality rate was 33.7/1000 births, nearly equally divided between fetal and early neonatal deaths, and 8.8% of the babies were of low birthweight. 36% of the perinatal deaths were antepartum stillbirths, and 60% of these weighed 2000 g or more. The 2nd most important cause was immaturity, which accounted for 31% of the deaths. In this latter group, 21% weighed 2000 g or more at birth. These findings, as well as the high birthweight-specific perinatal mortality rates, strongly suggest that there are deficiencies in the antenatal and delivery care in Pelotas that must be corrected promptly. Policies that should be implemented by health planners include: decentralization of antenatal care clinics; utilization in these clinics of the "at-risk" concept to identify women at high risk of delivering low birthweight babies, efforts to increase community participation and home visits in order to attract those pregnant women who do not attend clinics. In addition, it is mandatory that well-trained doctors (obstetricians and pediatricians) should be available 24 hours/day at the maternity hospitals to assist mothers and babies identified as being at high risk. (author's)     

Early life factors are determinants of female height at age 19 years in a population-based birth cohort (Pelotas, Brazil)

The purpose of this study was to investigate the influence of biological and social background on height of adolescent girls at age 19 y in the city of Pelotas, Southern Brazil. In 2001, a sample of the urban census tracts was visited and adolescent girls who were part of the Pelotas 1982 Birth Cohort Study were located. Standardized questionnaires were administered to the adolescents and their mothers. Height was measured using locally manufactured stadiometers; standardized protocols were employed. The information obtained in 2001 was combined with data collected in earlier phases of the study. The follow-up rate was 69% and 473 girls were studied in 2001. Multiple linear regressions were used to analyze the determinants of height. The height of the 19-y-old adolescents was 161.2+/-6.3 cm. The significant determinants of height were family income, maternal pre-gestational weight, maternal height, smoking during pregnancy, birth weight, height gain, and age at menarche. Birth weight was a more important predictor than weight gain during infancy or height gain between the ages of 2 and 4 y. Each 100 g in birth weight was associated with an increase of approximately 0.2 cm in the adolescent's height (P=0.001). The current findings reinforce the importance of early life factors in the determination of adult height.     

Socioeconomic situation and living conditions: comparison of two population-based cohorts from southern Brazil

Socioeconomic and family characteristics of two cohorts of babies born in 1982 and 1993 in Pelotas (Southern Brazil) were compared. There were 6,011 births in 1982 and 5,304 in 1993. In relation to family income, there were fewer poor babies in 1993; 60.8 % of the families earned less than 3 times the monthly minimum wage in 1993, as compared to 69.5% in 1982. Sanitary conditions also improved over the decade, and the proportion of families with running water and flush toilets increased by 10%. On the other hand, there were no changes in the proportion of single-parent families or availability of home appliances like radios, stoves, and refrigerators. The mean number of persons per household increased from 3.0 in 1982 to 3.2 in 1993. In general, comparison of the two birth cohorts in this city suggests an improvement in quality of living over the time period for families with newborns. This finding should be taken into account when studying the evolution of health indicators over the course of the decade.     

Developmental status at age 12 months according to birth weight and family income: a comparison of two Brazilian birth cohorts

Two cohorts of children born in the city of Pelotas, Southern Brazil, in 1993 and 2004, were compared in terms of neuro-psychomotor development at the age of 12 months. Children were evaluated using the Denver II screening test. Analyses were performed using the Poisson regression technique. The prevalence of suspected developmental delay fell from 37.1% in 1993 to 21.4% in 2004 and was inversely proportional to family income and birth weight. Among children born weighing under 2,000 g, there was a fourfold reduction in the prevalence of developmental delay between 1993 and 2004. With regard to family income, the poorest group showed the greatest reduction between the two cohorts--a 30% reduction in risk. Our results confirm the influence of income and birth weight on child development. The decrease in the prevalence of developmental delay in the last decade reflects, among other factors, improvements in neonatal care, increased coverage of developmental monitoring in the first year of life, and longer breastfeeding duration. Despite this reduction, the prevalence of developmental delay is still high, reinforcing the need for early diagnosis and intervention.     

The Pelotas birth cohort study, Rio Grande do Sul, Brazil, 1982-2001

Given the growing recognition of the importance of the life course approach for the determination of chronic diseases, birth cohort studies are becoming increasingly important. This paper describes the methods used in the 1982 Pelotas (Brazil) birth cohort study, one of the largest and longest studies of this type in developing countries. All 5,914 hospital births occurring in Pelotas in 1982 (over 99% of all deliveries) were studied prospectively. The main stages of the study took place in 1983, 1984, 1986, 1995, 1997, 2000, and 2001. More than two thousand variables are available for each subject who participated in all stages of the study. Recent phases of the study included the examination of 2,250 males when presenting for the army recruitment exam in 2000, the study of a 27% sample of men and women in 2001 through household visits, and the study of over 400 children born to the cohort women. Follow-up rates in the recent stages of the cohort were 78.9% for the army examination and 69.0% for the household visits. Ethnographic and oral health studies were conducted in sub-samples. Some recent results on blood pressure, adolescent pregnancy, and asthma are presented as examples of utilization of the data. Suggestions on lessons learned for other cohort studies are proposed.