Levels and determinants of early neonatal mortality in Natal, northeastern Brazil: results of a surveillance and case-control study

An institution-based surveillance and nested case-control study was conducted in Natal, Northeastern Brazil to estimate the level and determinants of early neonatal mortality. The early neonatal mortality rate was 25.5 per 1000 live-birth, 75% of early neonatal deaths were premature low birthweight infants, and the mortality rates were 591 and 318 per 1000 respectively, for preterm small for gestational age (PT-SGA) and preterm appropriate for gestational age (PT-AGA) infants. Mortality was 50 per 1000 for term low birthweight, and 8.6 for term normal birthweight AGA infants. In addition to prematurity and low birthweight, the main risk factors associated with early neonatal death were maternal smoking, complications during pregnancy or intrapartum, and inadequate antenatal care. The associations were weaker for prepregnancy factors such as single marital status or low maternal body weight, and no significant associations were observed with socioeconomic status. These findings suggest that in this population, efforts to reduce early neonatal death should focus on improved maternal care and the prevention of prematurity.     

The association of maternal low birthweight and infant low birthweight in a racially mixed population

The association between maternal low birthweight (LBW) and infant low birthweight has been explored in previous studies in mainly middle and upper income, Caucasian populations. This study investigated whether the association found in these populations is true in a racially mixed, low socio-economic group. A case-control methodology was used and estimates of association were derived by means of logistic regression analyses. Data were gathered for 167 LBW infant-mother dyads and 338 adequate weight infant-mother controls matched on race and parity. The odds of a LBW infant having a LBW mother were 80% more likely than for adequate weight infants (OR = 1.80, 95% CI 1.14-2.84). This association was stronger for Hispanic women and their infants than for Black or non-Hispanic White women and their infants. Women who were both preterm and LBW had the higher estimate of risk for infant LBW than women who were LBW due to intrauterine growth retardation (IUGR). As found in previous research, the estimate of association between maternal LBW and infant LBW was greater for those infants who were LBW due to IUGR than those who were LBW due to being premature. The question of whether maternal LBW is also associated with increased risk of neonatal mortality and morbidity is as yet left unanswered.     

Maternal education as a modifier of the association between low birthweight and infant mortality

Both low birthweight (LBW) and infant mortality rate (IMR) have been consistently shown to be associated with maternal level of educational attainment. This paper examines the mortality risk attributable to LBW in different levels of maternal education. Comprising the study population were 18,715 singleton live births to Jewish mothers ages 20-39, during the years 1977-1980 in the Negev (the southern part of Israel). Data were obtained from a linked record of birth and death certificates. As expected, proportions of LBW (less than 2500 grams) were inversely related to level of maternal education (12.2% in the lowest educational level, 7.9% and 8.0% in the two intermediate levels, and 7.2% in the highest educational level). The mortality risk attributed to LBW was found to be modified by maternal level of education. Mortality ratios standardized for maternal age and parity were computed, using educational level 3, where the lowest mortality rates were observed, as the standard population. Among LBW infants no significant differences were found across educational levels, except for the lowest educational level where only 69% of the expected number of deaths were observed. The survival advantage of LBW infants in the lowest educational level was observed both in the neonatal and the postneonatal periods. Among normal birthweight (NBW) infants, a statistically significant excess mortality was detected both in the highest and the lowest educational levels. The excess mortality of NBW infants in the highest level of maternal education was due to neonatal mortality (SMR = 2.2), while the excess mortality in this birthweight category in the lowest educational level occur mainly in the postneonatal period (SMR = 2.4).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence of low birth weight and its determinants in an urban resettlement area of Delhi

Birth weight remains an important factor affecting infant and child mortality. Many factors influence the occurrence of low birth weight (LBW). The present study was conducted to study the prevalence and determinants of LBW in an urban resettlement area of Delhi. A baseline survey was done to enroll all pregnant women in the area. These women were followed up every month till outcome. The prevalence of LBW was 39.1%. Occurrence of LBW was related to age, parity, weight and height of the mother. In multiple logistic regression analysis, mother's weight and parity alone emerged as significant variables. On further analysis, on adjusting for age, parity and birth weight were associated for the 20-35-year age group only. Thus, prevalence of LBW remains high in the urban under privileged of Delhi; maternal age, parity and weight and height are important determinants. Increasing age of first birth to more than 20 years can minimize effect of primi parity.     

Relationship Between Gestational Weight Gain and Birthweight Among Clients Enrolled in the Special Supplemental Nutrition Program for Women,Infants, and Children (WIC), Hawaii, 2003–2005

To investigate the relationship between gestational weight gain (GWG) and birthweight outcomes among a low-income population in Hawaii using GWG recommendations from the 2009 Institute of Medicine (IOM) guidelines. Data were analyzed for 19,130 mother-infant pairs who participated in Hawaii’s Special Supplemental Nutrition Program for Women, Infants, and Children from 2003 through 2005. GWG was categorized as inadequate, adequate, or excessive on the basis of GWG charts in the guidelines. Generalized logit models assessed the relationship between mothers’ GWG and their child’s birthweight category (low birthweight [LBW: <2,500 g], normal birthweight [2,500 g ≤ BW < 4,000 g], or high birthweight [HBW: ≥4,000 g]). Final models were stratified by prepregnancy body mass index (underweight, normal weight, overweight, or obese) and adjusted for maternal age, education, race/ethnicity, smoking status, parity, and marital status. Overall, 62 % of the sample had excessive weight gain and 15 % had inadequate weight gain. Women with excessive weight gain were more likely to deliver a HBW infant; this relationship was observed for women in all prepregnancy weight categories. Among women with underweight or normal weight prior to pregnancy, those with inadequate weight gain during pregnancy were more likely to deliver a LBW infant. Among the low-income population of Hawaii, women with GWG within the range recommended in the 2009 IOM guidelines had better birthweight outcomes than those with GWG outside the recommended range. Further study is needed to identify optimal GWG goals for women with an obese BMI prior to pregnancy.     

Perinatal mortality in Scotland: 1970-9.

An examination of the recent decline in perinatal mortality in Scotland during the 1970s showed that despite substantial changes in fertility and the demographic pattern of births, differences in the age, parity, and social class composition of the obstetric population in this decade accounted for just 7% of the overall improvement in perinatal mortality between 1970 and 1979. The general pattern of relative risks associated with maternal age, parity, and social class remained largely unchanged. Marginal changes in the birthweight distribution, however, were sufficient to account for 13% of the reduction in perinatal mortality. The low birthweight infant, especially those weighing under 1500 g, assumed increasing importance as a factor in perinatal mortality owing to a progressive worsening in the relative risk of perinatal mortality associated with low birth weight. Although regional differences in perinatal mortality persisted over this period, there occurred some lessening of the traditional inequality between western and eastern parts of the country. Finally, registered causes of perinatal mortality are reviewed. In the absence of other explanations the results of this analysis, collectively, suggest that much of the recent decline in perinatal mortality was perhaps due to changes in obstetric practice and in the clinical management of neonatal morbidity.     

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.     

Low birthweight, preterm, and small for gestational age babies in Scotland, 1981-1984.

STUDY OBJECTIVE--The aim was to examine the effect of maternal age, gravidity, marital status, previous perinatal deaths, and parental social class on babies born low birthweight, preterm, and small for gestational age. DESIGN--The study used data on discharge summaries from all maternity hospitals in Scotland. SETTING--The study was based on all singleton deliveries in Scotland. PARTICIPANTS--The analysis involved information on 259,462 singleton babies born during the four years 1981-84 in Scotland. MEASUREMENTS AND MAIN RESULTS--Previous perinatal death was found to be the strongest predictor for both preterm and low birthweight. Single mothers were at particularly high risk of having a small for gestational age baby and those who were previously married of having a preterm baby. Women aged less than 20 years old, those over 34 years old, nulligravidae, and those of parity 3 or more were also at increased risk of adverse pregnancy outcome. Mothers and fathers in manual social classes and those who could not be assigned a social class on the basis of their occupation were at increased risk for all three adverse outcomes studied. The babies of parents who were in manual occupations were twice as likely as those of parents in non-manual occupations to be small for gestational age and almost twice as likely to be low birthweight. CONCLUSIONS--Mother's social class is a risk factor for adverse pregnancy outcome independent of maternal age, parity, and adverse reproductive history, and also independent of father's social class. Information on both parents' occupations should be collected in maternity discharge systems.     

Social determinants of birthweight and length of gestation in Estonia during the transition to democracy

BACKGROUND: To investigate social variation in birthweight and length of gestation in Estonia in the period of transition to a democracy and market economy. METHODS: All live births resulting from singleton pregnancies reported to the Estonian Medical Birth Registry in 1992-1997 (n = 84, 629) were studied with respect to social variation in birthweight and preterm delivery (<37 weeks gestation). The results were adjusted for maternal age, parity, education, nationality, marital status, smoking in pregnancy, sex of the infant (and gestational age). RESULTS: Between 1992 and 1997, mean birthweight increased from 3,465g to 3,497g (P < 0.001) and the preterm rate fell from 5.8% to 5.1% (P = 0.001). Maternal education, marital status and nationality were all independently related to the mean birthweight and the risk of preterm birth. The mean difference in birthweight between children of mothers with basic and university education was 87 g (95% CI : 74-100). Children born to mothers of non-Estonian compared to Estonian nationality were on average 77 g lighter (95% CI: 70-84). While the effect of nationality and marital status on birthweight was relatively stable during the study period, differences in birth outcome by maternal education became stronger. CONCLUSIONS: The mean birthweight increased and the preterm rate decreased in Estonia as a whole during the transition. However, the improvements were not shared equally by all social groups. An increase in variation in birthweight by maternal education was particularly notable.     

WIC participation and pregnancy outcomes: Massachusetts Statewide Evaluation Project.

The effects of WIC prenatal participation were examined using data from the Massachusetts Birth and Death Registry. The birth outcomes of 4,126 pregnant women who participated in the WIC program and gave birth in 1978 were compared to those of 4,126 women individually matched on maternal age, race, parity, education, and marital status who did not participate in WIC. WIC prenatal participants are at greater demographic risk for poor pregnancy outcomes compare to all women in the same community. WIC participation is associated with improved pregnancy outcomes, including, a decrease in low birthweight (LBW) incidence (6.9 per cent vs 8.7 per cent) and neonatal mortality (12 vs 35 deaths), an increase in gestational age (40.0 vs 39.7 weeks), and a reduction in inadequate prenatal care (3.8 per cent vs 7.0 per cent). Stratification by demographic subpopulations indicates that subpopulations at higher risk (teenage, unmarried, and Hispanic origin women) have more enhanced pregnancy outcomes associated with WIC participation. Stratification by duration of participation indicates that increased participation is associated with enhanced pregnancy outcomes. While these findings suggest that birth outcome differences are a function of WIC participation, other factors which might distinguish between the two groups could also serve as the basis for alternative explanations.     

Socioeconomic factors and adolescent pregnancy outcomes: distinctions between neonatal and postneonatal deaths?

Socioeconomic factors and adolescent pregnancy outcomes: distinctions between neonatal and postneonatal deaths ?
Markovitz, B.P. , Cook, R. , Flick, L.H. , Leet, T.L. ( 2005 ) BMC Public Health , 5 , 79 . doi:10.1186/1471‐2458‐5‐79. URL http://www.biomedcentral.com/1471‐2458/5/79 Background Young maternal age has long been associated with higher infant mortality rates, but the role of socio‐economic factors in this association has been controversial. We sought to investigate the relationships between infant mortality (distinguishing neonatal from post‐neonatal deaths), socio‐economic status and maternal age in a large, retrospective cohort study. Methods We conducted a population‐based cohort study using linked birth‐death certificate data for Missouri residents during 1997–1999. Infant mortality rates for all singleton births to adolescent women (12–17 years, n = 10 131; 18–19 years, n = 18 954) were compared with those for older women (20–35 years, n = 28 899). Logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI) for all potential associations. Results The risk of infant (OR 1.95, CI 1.54–2.48), neonatal (1.69, 1.24–2.31) and post‐neonatal mortality (2.47, 1.70–3.59) were significantly higher for younger adolescent (12–17 years) than older (20–34 years) mothers. After adjusting for race, marital status, age‐appropriate education level, parity, smoking status, prenatal care utilization, and poverty status (indicated by participation in WIC, food stamps or Medicaid), the risk of post‐neonatal mortality (1.73, 1.14–2.64) but not neonatal mortality (1.43, 0.98–2.08) remained significant for younger adolescent mothers. There were no differences in neonatal or post‐neonatal mortality risks for older adolescent (18–19 years) mothers. Conclusions Socio‐economic factors may largely explain the increased neonatal mortality risk among younger adolescent mothers but not the increase in post‐neonatal mortality risk.     

Risk factors for infant mortality from diseases in Japan 1995-98

OBJECTIVE: Since 1995, additional information (i.e. birth weight, singleton/multiple births, gestational weeks, maternal age, maternal parity and stillbirth experience) has been required for certificates of infant (less than 1 year of age) death from diseases in Japan. The present study examined the effects of biological, demographic and social variables, as reported on birth and death certificates, on infant, neonatal and postneonatal mortality in Japan. METHODS: Using data from vital statistics between 1995 and 1998, more than 4,787,000 livebirths and 16,000 infant deaths from diseases were analyzed. Univariate and multivariate analyses with the Poisson regression model were employed to assess the effects of variables on infant, neonatal and postneonatal mortality by singleton and multiple livebirths separately. RESULTS: The infant mortality rates from diseases were 3.2/1000 for singleton livebirths and 17.7/1000 for multiple livebirths. In singleton livebirths, low birth weight, infant born in earlier years, being a male infant, employment status as "unemployed or unknown", short gestational weeks, late birth in multiparity and maternal stillbirth experience were all significantly related to increased risk of neonatal and postneonatal deaths. Teenage mother were also at high risk of postneonatal deaths. Regional differences were observed. Compared with singleton livebirths, birthweight-specific mortality rates in multiple livebirths were relatively low among infants weighing under 2500 g. In multiple livebirths, elevated risk of death was associated with low birth weight, infant born in earlier years, employment status as "unemployed or unknown" and short gestational weeks. However, late birth in multiparity was related to a reduced risk of death, and maternal stillbirth experience was not a significant variable. CONCLUSION: This study provided the first quantitative estimate of risk of infant mortality from diseases in Japan. Since a more detailed elucidation of actual conditions and risk factors of infant deaths by vital statistics has become possible, efficient measures for improvement of infant mortality are to be expected.     

低出生体重与产前检查质量的回顾性分析

目的 探讨新生儿低出生体重(LBW)(出生体重＜2500 g)发生率与产前检查质量的关系.方法 采用Kessner's评定方法,对2008年1月至2009年12月在西安交通大学医学院第一附属医院产科产前检查的2964例单胎活产孕妇中,进行《产前检查问卷》调查.剔除缺项≥5项的问卷,共计回收有效问卷2928份,回收率为98.79％.对符合纳入标准的2928例单胎活产儿孕妇的产前检查质量进行评价.按照产前检查质量标准,将其分为充分组(n=1262)、居中组(n=1502)和不足组(n=164).采取回顾性分析方法于产后(2～7)d,依照《孕产妇产前检查手册》或门诊及住院病历记录3组孕妇的一般情况及其产前检查、孕期患病和分娩等情况.采用非条件logistic逐步回归分析法分析与LBW发生的相关危险因素及其与产前检查质量的关系(本研究遵循的程序符合本院人体试验委员会所制定的伦理学标准,得到该委员会批准,征得受试对象知情同意并与之签署临床研究知情同意书).3组孕妇孕前体重指数(BMI)、本次妊娠胎数比较,差异无统计学意义(P＞0.05).结果 LBW儿发生率在充分组、居中组和不足组分别为3.49％(44/1262),5.26％(79/1502)和19.51％ (32/164).产前检查不足组LBW儿发生率最高,与其他两组比较,差异有统计学意义(P＜0.01).LBW儿发生的相关危险因素包括:①孕妇年龄;②婚姻状况;③是否有妊娠合并症;④分娩地点;⑤孕期体重增加;⑥分娩孕周等,与产前检查质量密切相关(r=0.83,0.69,0.85,-0.68,-0.71,-0.74;P＜0.05).LBW儿发生与产次无相关性(r=0.26,P＞0.05).本组LBW儿与正常体重儿(≥2500 g)母亲的产前检查质量、年龄、婚姻状况、产次、是否有妊娠合并症、分娩地点、孕期体重增加、分娩孕周等比较,差异有统计学意义(x2=96.05,58.84,21.41,52.38,38.10,33.44,66.32,258.42;P＜0.05).与正常体重儿比较,LBW儿母亲孕期平均接受产前检查次数较少[(7.6±3.1)次vs.(5.4±2.9)次;t=9.16,P＜0.01];产前检查充分组较居中组LBW儿发生率低(OR=0.51,95％CI:0.35～0.72).调整孕妇年龄、孕期体重增加、妊娠并发症、产前检查医院类别及分娩孕周后,产前检查次数较少,仍是LBW儿发生的危险因素(OR=4.56,95％CI:3.02～6.84).结论 采用Kessner's评定方法评估产前检查质量相对客观准确,产前检查次数较少,是LBW儿发生的独立危险因素.     

Changing patterns of inequality in birthweight and its determinants: a population-based study, Scotland 1980-2000

Birthweight is used as an indicator of individual and population health and is known to be strongly correlated with adult cardiovascular disease. This paper uses routinely collected maternity discharge data from Scotland between 1980 and 2000 to look at birthweight trends and the changes in the distribution of maternal risk factors for birthweight. We also examine the contributions of each of the risk factors to birthweight trends and investigate whether there has been a reduction in inequality in birthweight over time. Data from 1,282,172 singleton live births were used in the analysis. Both mean birthweight and low birthweight (LBW:<2500 g) were used as outcomes. The risk factors studied were maternal age, parity, maternal height, marital status and occupational social class of the father. The slope and relative indices of inequality were used to measure the change in inequalities over time. Mean birthweight increased from 3320 g in 1980 to 3410 g in 2000, while the percentage LBW decreased slightly from 5.7% in 1980 to 5.4% in 2000. The prevalence of many risk factors changed; there has been an increase in the proportion of older mothers, single mothers, taller mothers and mothers with undetermined social class. Although most risk factors had a significant change in effect over time, the inequalities in birthweight between groups did not appear to diminish over time. Both the slope and relative index of inequality had a quadratic relationship over time, with the inequalities in birthweight being greatest in the early 1980s and late 1990s.     

Major improvements, but persisting inequalities in infant survival in Estonia 1992-2002

BACKGROUND: Inequality in adult health increased in Estonia during the transition period after 1991. We examined inequality in infant survival from 1992 to 2002. METHODS: All 132 854 singleton live births reported to the Estonian Medical Birth Registry in 1992-2001 were linked to the Estonian Mortality Database. The effect of mother's education, nationality, marital status, and place of residence on neonatal (0-27 days) and post-neonatal (28-364 days) death was evaluated in logistic regression with adjustments for maternal age, parity, smoking, sex of the infant, birth weight, and gestational age. RESULTS: Infant mortality decreased substantially. Risk of death in neonatal period was lowest in Tartu, with a decline from 4.9/1000 in infants born in 1992-1996 to 2.1/1000 in those born in 1997-2001. Decline in neonatal mortality in other regions was from 9.2/1000 to 5.1/1000. Persisting regional differences were unexplained by mothers' nationality, education, or marital status, or the infants' length of gestation. Decline in post-neonatal mortality was less marked and although risk differences between different socio-economic groups decreased, mothers' marital status and education in particular remained strongly associated with risk of post-neonatal death [odds ratio for infants born to mothers with basic or lower education compared to university education 3.70 (95% confidence interval 2.34-5.85) in 1992-1996 and 3.56 (2.06-6.14) in 1997-2001]. CONCLUSIONS: Infant survival improved appreciably in Estonia after 1991 and risk differences between social groups decreased. The improvements were not accompanied by reduction in the strength of the effects of social characteristics on infant death measured as risk ratios.     

Predictors of foetal and neonatal mortality in Cura?ao, Netherlands Antilles. A multivariate analysis

In Cura?ao a systematic and comprehensive investigation of numerous factors, potentially associated with an increased risk of foetal and neonatal mortality, was carried out in a 2-year period (1984-85). The inquiry was restricted to singleton births. Data on 205 women who experienced pregnancy loss were compared with those on 913 women who did not sustain foetal or neonatal loss. Data comprised information on maternal characteristics, clinical course of pregnancy and delivery, and neonatal characteristics. Of 130 factors measured, 14 were entered into a multivariate analysis. From the analysis 5 risk factors emerged as significant predictors of mortality: gestational age, birth weight, sex, foetal presentation and congenital anomalies. Factors such as social class, marital status, maternal age and parity were not associated with an increased risk of foetal and neonatal mortality in Cura?ao.     

Multiethnic variations in the pregnancy outcomes of military dependents.

OBJECTIVES. We examined the pregnancy outcomes of three ethnic groups: African-American Blacks, non-Hispanic Whites, and Filipinos. In an attempt to reduce ethnic dissimilarities in parental employment and access to health care, this investigation compared the single-live-birth outcomes of married, adult women who resided in the state of Hawaii and who indicated that their spouse was on active-duty status in the US military. METHODS. The data for this study were obtained from the 1979-1989 Hawaii vital-record file that provides linked live birth-infant death information. Multiple logistic regression was used to calculate odds ratios for the independent effects of maternal factors on low birthweight and neonatal mortality. RESULTS. Significant differences in maternal age, maternal education, paternal education, parity, hospital of delivery, and use of prenatal care were observed among the ethnic groups. The results of a logistic regression analysis of low birthweight indicated significantly higher risks for Filipinos and Blacks compared with Whites. For very low birthweight, only an increased risk for Blacks was observed. No ethnic differences in neonatal mortality were found. CONCLUSIONS. This investigation revealed more comparable infant mortality experiences among the ethnic groups in spite of persistent birthweight differences.     

Low birthweight and prematurity in relation to paternal factors: a study of recurrence.

BACKGROUND: The importance of paternal determinants in the occurrence of low birthweight and prematurity is not well known. We investigated these outcomes in siblings and paternal half siblings as a function of changes in putative external determinants between two births in fathers who had experienced the birth of a premature and/or low birthweight (PTB/LBW) infant. METHODS: All fathers who, between 1980 and 1992, had an infant born before 37 completed weeks' gestation or weighing <2500 g and a following child were studied. We identified 14 147 pairs of siblings from Danish national registers. The recurrence risk was studied in three sub-cohorts defined by the outcome in the index child (PTB only, PTB/LBW, LBW only). We estimated the recurrence risk in the younger sibling according to changes of female partner, municipality type, occupation, and father's social status. RESULTS: The overall recurrence risk was 16.7% for preterm delivery and 16.8% for LBW. Changing female partner was, as expected, associated with a reduction in the recurrence risk for both outcomes (RR = 0.40; 95% CI: 0.27-0.60 for preterm delivery and RR = 0.38; 95% CI : 0.26-0.56 for LBW). None of the other studied factors was associated with changes in the recurrence risk. Fathers who changed partner had offspring with similar birthweight and gestational length between the three sub-cohorts, while a difference was evident in offspring to fathers whose female partner was unchanged. CONCLUSIONS: We did not identify any paternal factor of importance in the occurrence of LBW and preterm delivery.     

Trends in low birth weight infants and changes in Baltimore's childbearing population, 1972–77

Linked birth and death records provided the population for a study of trends in low birth weight (LBW) rates in Baltimore between 1972 and 1977 and of the effect of changes in the characteristics of the childbearing population on these trends. The impact of shifts in the birth weight distribution on neonatal mortality rates was also investigated. Trends were analyzed for unstandardized LBW rates as well as for rates standardized on the distributions of maternal age, education, gravidity, prior pregnancy losses, and marital status.Between 1972 and 1977, the 1,500 and 2,000 gm rates rose significantly by approximately 1 infant per 1,000 live births per year among whites and 2 infants per 1,000 live births among nonwhites. Despite declines in rates for most weights, the effect of these increases was a rise in neonatal mortality rates for both races, but especially for nonwhites.The population of women delivering in Baltimore in 1977 became slightly older, slightly more educated, and of higher gravidity than in 1972, but these changes had little impact on yearly fluctuations in LBW rates. In contrast, increases in births to unmarried women and to women with at least one prior pregnancy loss were related to rising LBW rates. For both races, standardization on marital status and prior pregnancy losses diminishes the increase in the LBW rate over the study period, especially when standardization is performed simultaneously for both variables. These findings hold within maternal age, education, and gravidity groups. However, the LBW rates for nonwhite teenage mothers and for nonwhite women with 12 years of less education increased significantly over the study period, regardless of standardization.     

Racial differences in birthweight for gestational age and infant mortality in extremely-low-risk US populations

Using national data, we develop and contrast the birth-weight percentiles for gestational age by infants of extremely-low-risk (ELR) White and African-American women and examine racial differences in the proportion of small-for-gestational-age (SGA) births. We then scrutinise racial variations in infant mortality rates of the infants of ELR women. We further compare the infant mortality rates of infants at or below the 10th percentile of birthweight for gestational age of each race group to determine whether infants with similar restricted fetal growth have comparable risks of subsequent mortality. Single live births, 34-42 weeks' gestation, to White and African-American US-resident mothers were selected from the 1990-91 US Linked Live Birth--Infant Death File (n = 4,360,829). Extremely-low-risk mothers were defined as: married, aged 20-34 years, 13+ years of education, multiparae, with average parity for age, adequate prenatal care, vaginal delivery, and no reports of medical risk factors, tobacco use or alcohol use during pregnancy. Marked racial variation in birthweight percentiles by gestational age was evident. Compared with ELR White mothers, the risk of an SGA infant was 2.64 times greater for ELR African-American mothers and the risk of infant mortality was 1.61 times greater. For the ELR group, the infant mortality rates of African-American and White infants at or below the 10th percentile of birthweight for gestational age of their respective maternal race group were essentially identical after controlling for gestational age. In conclusion, race differences in fetal growth patterns remained after controlling for risk status. Efforts to remove racial disparities in infant mortality will need to develop aetiological pathways that can explain why African-Americans have relatively higher rates of preterm birth and higher infant mortality rates among term and non-SGA infants.