Risk factors for neonatal mortality in rural areas of Bangladesh served by a large NGO programme

Neonatal deaths account for about half of all deaths among children under 5 years of age in Bangladesh, making prevention a major priority. This paper reports on a study of neonatal deaths in 12 areas of Bangladesh served by a large NGO programme, which had high coverage of reproductive health outreach services and relatively low neonatal mortality in recent years. The study aimed to identify the main factors associated with neonatal mortality in these areas, with a view to developing appropriate strategies for prevention. A case-control design was adopted for collection of data from mothers whose children, born alive in 2003, died within 28 days postpartum (142 cases), or did not (617 controls). Crude and adjusted odds ratios (AOR) were calculated as estimates of relative risk for neonatal death, using 'neighbourhood' controls (241) and 'non-neighbourhood' controls (376). A similar proportion of case and control mothers had received NGO health education and maternal health services. The main risk factors for neonatal death among 122 singleton babies, based on the two sets of controls, were: complications during delivery [AOR, 2.6 (95% CI: 1.5-4.5) and 3.1 (95% CI: 1.8-5.3)], prematurity [AOR, 7.2 (95% CI: 3.6-14.4) and 8.3 (95% CI: 4.2-16.5)], care for a sick neonate from an unlicensed 'traditional healer' [AOR, 2.9 (95% CI 0.9-9.5 and 5.9 (95% CI: 1.3-26.3)], or care not sought at all [AOR, 23.3 (95% CI: 3.9-137.4)]. The strongest predictor of neonatal death was having a previous sibling not vaccinated against measles [AOR, 5.9 (95% CI: 2.2-15.5) and 12.0 (95% CI: 4.5-31.7)]. The findings of this study indicate the need for identification of babies at high risk and early postpartum interventions (40.2% of the deaths occurred within 24 hours of delivery). Relevant strategies include special counselling during pregnancy for mothers with risk characteristics, training birth attendants in resuscitation, immediate postnatal check-up in the home for high-risk babies identified at delivery, advice for mothers on appropriate care-seeking for sick babies, improving the capacity of sub-district hospitals for emergency obstetric and newborn care, and promotion of institutional deliveries.     

Ethnic differences in the incidence of the sudden infant death syndrome (SIDS) in Victoria, Australia 1985–1989

Summary. In order to describe ethnic differences in the incidence of the sudden infant death syndrome (SIDS) records of all livebirths in the State of Victoria, Australia, 1985–1989, excluding those who died in the first month of life, were linked to death certificates. Cases were defined as infants dying with a diagnosis of SIDS between 1 month and 1 year of age ( n = 601) from the cohort of 308052 neonatal survivors. Ethnicity was defined by the mother's country of birth. The SIDS incidence was 2.04/1000 in infants of Australian-born mothers. The relative risk of SIDS was 0.28 (95% confidence interval (CI) 0.15,0.55) in infants whose mothers had been born in Southern Europe and 0.48 (95% CI 0.29, 0.78) in infants whose mothers had been born in Asia. SIDS in infants of Australian-born mothers was associated with low maternal age, high parity, marital status other than married, male sex, multiple birth, low birthweight and preterm birth. After adjustment for those factors in a case-control analysis using a logistic regression model the adjusted odds ratio for SIDS was 0.34 (95% CI 0.17, 0.69) comparing infants whose mothers were born in Southern Europe with infants of Australian-born mothers, and 0.60 (95% CI 0.35, 1.04) for infants whose mothers were born in Asia, compared with infants of the Australian-born. Thus there are substantial ethnic differences in SIDS which are not explained by the classic social and perinatal risk factors.     

No fathers' names: a risk factor for infant mortality in the State of Georgia, USA

Many studies have explored maternal and infant factors as risks for infant mortality, but little attention is given to paternal factors. In Georgia, listing a father's name on the birth certificate is optional for married couples and possible after paternal acknowledgment for unmarried couples. The authors evaluated father's name reporting as a paternity measure and risk for infant mortality. Using the linked 1989-1990 birth and death certificates of singleton Georgia infants to calculate relative risks (RRs), infant mortality rates for 38,943 infants with no father's names listed were compared to rates for 178,100 with father's names listed. Compared with the rate for married women listing names, the death rates were higher for unmarried mothers not listing fathers (relative risk, RR = 2.5; 95% CI 2.3-2.7), unmarried mothers listing fathers (RR = 1.4; 95% CI 1.3-1.6), and married women not listing fathers (RR = 2.3; 95% CI 1.6-3.1). Increased risks remained after stratifying by maternal race, age, adequacy of prenatal care and medical risks; and congenital malformations, birthweight, gestational age, and small-for-gestational age. Using logistic regression to examine for effect modification and to adjust for these factors together, the adjusted relative risks for death varied across different groups without fathers' names, regardless of marital status. For example, it remained statistically higher for infants with no father listed and without effect-modifying conditions such as low birthweight (estimated RR = 2.0; 95% CI 1.6-2.4). Although these findings suggest paternal involvement, as measured by listing fathers' names, is protective against low birthweight and infant mortality, further evaluation is needed.     

Association between number of children and mortality of mothers: results of a 37-year follow-up study

PurposeTo examine the association between parity and long-term, all-cause mortality and mortality owing to specific causes in women.MethodsThis prospective population-based study included 40,454 mothers who gave birth in Western Jerusalem, Israel, to 125,842 children and were followed for an average of 37 years after the birth of their first child. Cox proportional hazards models were used to evaluate long-term total and specific-cause mortality of women by their parity.ResultsWe found a U-shaped relationship between the number of offspring and risk of all-cause mortality in mothers. After adjustment for sociodemographic characteristics and maternal health and obstetric conditions, higher mortality rates were observed for mothers of 1 child (hazard ratio [HR], 1.18; 95% confidence interval [CI], 1.04–1.4), mothers of 5 to 9 children (HR, 1.21; 95% CI, 1.09–1.33), and mothers of 10 or more children (HR, 1.49; 95% CI, 1.12–1.99) compared with mothers of 2 to 4 children. Mortality risk from specific causes including coronary disease, circulatory disease, and cancer were increased for multiparous women.ConclusionsIn this long-term follow-up study, there was an association between number of children and mortality risk for mothers. These findings suggest that maternal pregnancies and postnatal characteristics as reflected by number of children may have consequences for long-term maternal health.     

Mortality risk of small infants varies with their mother's birthweight and race

We analysed a transgenerational linked birth file to investigate the relationship between maternal birthweight and infant birthweight-specific mortality risk for white and African American infants. Birth records of 267,303 infants born between 1989 and 1991 were linked to records of their mothers, born between 1956 and 1976, and to their own death certificates for those dying in the first year. The means, standard deviations and z-scores were calculated for each race- and generation-specific birthweight distribution. Investigators then analysed the mortality of very small infants (birthweight at least two standard deviations below their mean) for three maternal birthweight categories. Over half of the infant deaths involved births with weights more than two standard deviations below the relevant population mean birthweight (comprising 4.2% of white and 6.9% of African American births respectively). African American infants experienced higher mortality rates at all levels of standardised birthweight, from z-scores of -3 to +3. The relative risk of mortality associated with very small infant size was less for infants delivered to smaller birthweight mothers when compared with those whose mothers were average sized or large at birth. This differential effect was confined to neonatal deaths and was more prominent in the white subpopulation.     

Early mortality among aboriginal and non-aboriginal women who had a preterm birth in Western Australia: A population-based cohort study

Background

Having a preterm (<37 weeks' gestation) birth may increase a woman's risk of early mortality. Aboriginal and Torres Strait Islander (hereafter Aboriginal) women have higher preterm birth and mortality rates compared with other Australian women.

Objectives

We investigated whether a history of having a preterm birth was associated with early mortality in women and whether these associations differed by Aboriginal status.

Methods

This retrospective cohort study used population-based perinatal records of women who had a singleton birth between 1980 and 2015 in Western Australia linked to Death Registry data until June 2018. The primary and secondary outcomes were all-cause and cause-specific mortality respectively. After stratification by Aboriginal status, rate differences were calculated, and Cox proportional hazard regression was used to estimate adjusted hazard ratios (HR) and 95% confidence intervals (CI) for all-cause and cause-specific mortality.

Results

There were 20,244 Aboriginal mothers (1349 deaths) and 457,357 non-Aboriginal mothers (7646 deaths) with 8.6 million person-years of follow-up. The all-cause mortality rates for Aboriginal mothers who had preterm births and term births were 529.5 and 344.0 (rate difference 185.5, 95% CI 135.5, 238.5) per 100,000 person-years respectively. Among non-Aboriginal mothers, the corresponding figures were 125.5 and 88.6 (rate difference 37.0, 95% CI 29.4, 44.9) per 100,000 person-years. The HR for all-cause mortality for Aboriginal and non-Aboriginal mothers associated with preterm birth were 1.48 (95% CI 1.32, 1.66) and 1.35 (95% CI 1.26, 1.44), respectively, compared with term birth. Compared with mothers who had term births, mothers of preterm births had higher relative risks of mortality from diabetes, cardiovascular, digestive and external causes.

Conclusions

Both Aboriginal and non-Aboriginal women who had a preterm birth had a moderately increased risk of mortality up to 38 years after the birth, reinforcing the importance of primary prevention and ongoing screening.     

人类免疫缺陷病毒感染孕产妇所产婴儿死亡的影响因素分析

目的 了解我国获得性免疫缺陷综合征(AIDS)高流行地区人类免疫缺陷病毒(HIV)感染孕产妇所产婴儿死亡的影响因素.方法 结合2004年建立的HIV感染孕产妇及所产婴儿随访研究队列,于2008年8-11月对我国4省7县区2004年1月至2007年11月HIV感染孕产妇所产婴儿的死亡状况及其影响因素进行调查.实际收集了498对HIV感染孕产妇及所产婴儿的相关信息.采用单因素和多因素Cox比例风险模型对HIV感染孕产妇所产婴儿死亡的影响因素进行分析.结果 498名婴儿,总观察人年数为406.22人年,死亡45例,死亡密度为110.78/1000人年.单因素分析结果显示,母亲孕产期处于AIDS前期或发病期(RR=1.971,95%CI值:1.143～3.396)、孕产妇生存状况(RR=3.062,95%CI值:1.097～8.550)、经产妇(RR=0.517,95%CI值:0.278～0.961)、自然分娩(RR=0.561,95%CI值:0.345～0.910)、早产(RR=5.302,95%CI值:2.944～9.547)、低出生体重(RR=4.920,95%CI值:2.691～8.994)、母子预防性服用抗逆转录病毒药物(RR=0.227,95%CI值:0.121～0.428)及婴儿感染HIV(RR=5.870,95%CI值:3.232～10.660)等因素影响HIV感染孕产妇所产婴儿的死亡.进一步的多因素分析显示,处于AIDS前期或发病期的孕产妇较处于AIDS潜伏期者所产婴儿死亡危险增加(RR=6.99,95%CI值:1.92～25.64);孕产期CD4~+T淋巴细胞计数低于200个/μl的孕产妇,所产婴儿发生死亡的危险增加(RR=2.05,95%CI值:1.01～4.15);母子未预防性服用抗逆转录病毒药物增加婴儿死亡的危险(RR=6.17,95%CI值:1.62～23.26);早产婴儿死亡危险是足月产婴儿的2.87倍(95%CI值:1.12～7.35);HIV感染婴儿死亡危险是非HIV感染婴儿的9.87倍(95%CI值:3.81～25.62).结论 提高HIV感染孕产妇自身免疫力,降低HIV母婴传播率及HIV感染孕产妇所产婴儿早产、低出生体重的发生率有助于降低婴儿死亡率.     

Causes of Mortality and Risk Factors for Injury Mortality Among Children in the Agricultural Health Study

Abstract

Farm children face unique health risks due to sharing their residential environment with hazardous machinery and materials. Causes of mortality among farm children have not been comprehensively described.

Objective: In the Agricultural Health Study (AHS) cohort, we examined causes of mortality among 21,360 children in Iowa and North Carolina between 1975 and 1998.

Methods: We matched identifying information for children provided by mothers on self-administered questionnaires to state death registries (1975–1998). Data on farm and family characteristics were provided by parents via enrollment questionnaires (1993–1997). Standardized mortality ratios (SMRs) were calculated, using state mortality data to generate expected deaths. We used logistic regression to examine parent, child and farm characteristics associated with injury mortality.

Results: There were 162 deaths in Iowa (SMR = 0.69; 95% confidence interval (CI) = 0.60, 0.81) and 26 deaths in North Carolina (SMR = 0.42; 95%CI = 0.28, 0.61) in children aged 0–19 years. This deficit was largely due to deaths in the first year of life. Although deaths from overall unintentional injury were not increased, excess agricultural machinery mortality was observed in Iowa (SMR = 9.25; 95% CI = 5.12, 16.70). In case-control comparisons, maternal age less than 25 years at child's birth (OR = 2.17; 95%CI = 1.05, 4.49) and having more than 2 children in the family (OR = 2.79; 95%CI = 1.47, 5.30) were associated with increased child injury mortality. For children under 14 years, participation in farm work was associated with increased risk of agricultural machine-related mortality (OR = 3.92; 95% CI = 1.04, 14.78).

Conclusions: Parent and child characteristics associated with child injury mortality could be used to target farm safety interventions.     

Residual confounding explains the association between high parity and child mortality

Background

This study used data from recent Demographic and Health Surveys (DHS) to examine the impact of high parity on under-five and neonatal mortality. The analyses used various techniques to attempt eliminating selection issues, including stratification of analyses by mothers’ completed fertility.

Methods

We analyzed DHS datasets from 47 low- and middle-income countries. We only used data from women who were age 35 or older at the time of survey to have a measure of their completed fertility. We ran log-binominal regression by country to calculate relative risk between parity and both under-five and neonatal mortality, controlled for wealth quintile, maternal education, urban versus rural residence, maternal age at first birth, calendar year (to control for possible time trends), and birth interval. We then controlled for maternal background characteristics even further by using mothers’ completed fertility as a proxy measure.

Results

We found a statistically significant association between high parity and child mortality. However, this association is most likely not physiological, and can be largely attributed to the difference in background characteristics of mothers who complete reproduction with high fertility versus low fertility. Children of high completed fertility mothers have statistically significantly increased risk of death compared to children of low completed fertility mothers at every birth order, even after controlling for available confounders (i.e. among children of birth order 1, adjusted RR of under-five mortality 1.58, 95% CI: 1.42, 1.76). There appears to be residual confounders that put children of high completed fertility mothers at higher risk, regardless of birth order. When we examined the association between parity and under-five mortality among mothers with high completed fertility, it remained statistically significant, but negligible in magnitude (i.e. adjusted RR of under-five mortality 1.03, 95% CI: 1.02-1.05).

Conclusions

Our analyses strongly suggest that the observed increased risk of mortality associated with high parity births is not driven by a physiological link between parity and mortality. We found that at each birth order, children born to women who have high fertility at the end of their reproductive period are at significantly higher mortality risk than children of mothers who have low fertility, even after adjusting for available confounders. With each unit increase in birth order, a larger proportion of births at the population level belongs to mothers with these adverse characteristics correlated with high fertility. Hence it appears as if mortality rates go up with increasing parity, but not for physiological reasons.

     

Does participation in a nurse visitation programme reduce the frequency of adverse perinatal outcomes in first-time mothers?

Children First (C1), a nurse home visitation programme for first-time mothers, was implemented statewide in Oklahoma in mid-1997. The objective of this study was to compare the risks of low (< 2500 g) and very low birthweight (< 1500 g), preterm (< 37 weeks) and very preterm (< 30 weeks) deliveries and infant mortality between mothers participating and not participating in C1. All 239,466 Oklahoma birth certificates were reviewed. The C1 and birth certificate databases were matched to identify C1 participants. Mother's age at delivery, education level, race, marital status, prior pregnancy loss or pregnancy risk factors, birthweight and gestational age at delivery were measured from the birth certificates. Death certificates were matched to the birth certificates to identify infant deaths. A Bayesian multivariable logistic regression was used to analyse the data. Among single mothers without pregnancy risk factors, the risks of all study outcomes were lower for participants in C1: adjusted odds ratio (aOR) 0.89, [95% Bayesian Credible Interval (BCI) 0.79, 1.00] for preterm delivery; aOR 0.71, [95% BCI 0.50, 0.98] for very preterm delivery; aOR 0.86, [95% BCI 0.75, 0.98] for low birthweight; aOR 0.77, [95% BCI 0.56, 1.02] for very low birthweight and aOR 0.36, [95% BCI 0.17, 0.63] for infant mortality. These risk reductions were not observed among married mothers. In both single and married mothers, the presence of pregnancy risk factors reduced the impact of C1 on lowering the risk of low birthweight and preterm deliveries. The C1 programme targets young, pregnant women of low socio-economic level. We found that among single mothers, the risks of perinatal adverse outcomes are reduced or similar to those found in non-participating mothers. A reduced effect of C1 in the presence of pregnancy risk factors may be because mothers with pregnancy risk factors who did not participate in C1 received better prenatal care, or that C1 interventions do not impact these particular factors. C1 shows promise in reducing infant mortality in single mothers. Lower incidence of preterm and very preterm deliveries is especially interesting and future analyses should focus on isolating programme components specifically associated with influencing these outcomes.     

Early childhood mortality from community-acquired infections.

In this study, the authors identified maternal and child characteristics that were independent predictors of death from infectious diseases acquired in the community and determined if these factors could be used to identify groups of children with excess risk of mortality from infection. A historical cohort study was conducted of children less than 5 years of age between 1985 and 1994 (the study period), who were born in Tennessee, and had complete information on their birth certificates. The primary outcome was death from infection identified from death certificates and confirmed through medical record review. Among the 1,014,976 children less than 5 years of age, who contributed 3,351,568 child-years of follow-up, there were 247 deaths from infections (7.4 deaths from infections per 100,000 child-years). Respiratory infections accounted for approximately one half of the deaths. Children having three or more older siblings or birth weight of less than 1,500 g had a 3-fold and 10-fold increased risk of death from infection, respectively, while children with both characteristics had a nearly 20-fold increased risk that persisted beyond the first year of life. Interventions should be focused on prevention of these infections in vulnerable children. At-risk children should be targeted for careful follow-up and early hospitalization when signs of infection develop.     

Racial disparity in pregnancy-related mortality following a live birth outcome

PURPOSE: African-American women have a 2- to 4-fold increased risk of pregnancy-related death compared with Caucasian women. We conducted this study to determine if differences in a combination of socioeconomic and medical risk factors may explain this racial disparity in pregnancy-related death. METHODS: Pregnancy-related deaths of African-American (N=60) and Caucasian (N=47) women were identified from review of pregnancy-associated deaths (N=400) ascertained through cause of death on death certificates, electronic linkage of birth and death files, and review of the hospital discharge database for the State of North Carolina, during the period between 1992 and 1998. Controls (N=3404) were randomly selected from all live births for the same 7-year period. Logistic regression was used to model the association between race and pregnancy-related death. RESULTS: The unadjusted odds ratio (OR) for pregnancy-related death for African-Americans compared with Caucasians was 3.07 (95% confidence interval [CI], 2.08, 4.54). After controlling for gestational age at delivery, maternal age, income, hypertension, and receipt of prenatal care, African-American race remained a significant predictor variable (OR 2.65 [95% CI 1.73, 4.07]). CONCLUSIONS: Our analysis confirms that there is a strong association between race and pregnancy-related death, even after adjusting for potential predictors and confounders.     

Impact of the Red River Catastrophic Flood on Women Giving Birth in North Dakota, 1994–2000

To document changes in birth rates, birth outcomes, and pregnancy risk factors among women giving birth after the 1997 Red River flood in North Dakota. We analyzed detailed county-level birth files pre-disaster (1994–1996) and post-disaster (1997–2000) in North Dakota. Crude birth rates and adjusted fertility rates were calculated. The demographic and pregnancy risk factors were described among women delivering singleton births. Logistic regression was conducted to examine associations between the disaster and low birth weight (<2,500 g), preterm birth (<37 weeks), and small for gestational age infants adjusting for confounders. The crude birth rate and direct-adjusted fertility rate decreased significantly after the disaster in North Dakota. The proportion of women giving birth who were older, non-white, unmarried, and had a higher education increased. Compared to pre-disaster, there were significant increases in the following maternal measures after the disaster: any medical risks (5.1–7.1%), anemia (0.7–1.1%), acute or chronic lung disease (0.4–0.5%), eclampsia (0.3–2.1%), and uterine bleeding (0.3–0.4%). In addition, there was a significant increase in births that were low birth weight (OR 1.11, 95% CI 1.03–1.21) and preterm (OR 1.09, 95% CI 1.03–1.16) after adjusting for maternal characteristics and smoking. Following the flood, there was an increase in medical risks, low birth weight, and preterm delivery among women giving birth in North Dakota. Further research that examines birth outcomes of women following a catastrophic disaster is warranted.     

Pregnancy outcome in more than 5000 births to women with viral hepatitis: a population-based cohort study in Sweden

Previous studies have shown inconsistent results with respect to hepatitis B (HBV), hepatitis C (HCV) and pregnancy outcome. The aim of this study was to investigate pregnancy outcome in women with HBV or HCV. In a nationwide cohort of births between 2001 and 2011 we investigated the risks of adverse pregnancy outcomes in 2990 births to women with HBV and 2056 births to women with HCV using data from Swedish healthcare registries. Births to women without HBV (n = 1090 979), and births without HCV (n = 1091 913) served as population controls. Crude and adjusted relative risks (aRR) were calculated using Poisson regression analysis. Women with HCV were more likely to smoke (46.7 vs. 8.0%) and to have alcohol dependence (18.9 vs. 1.3%) compared with population controls. Most women with HBV were born in non-Nordic countries (91.9%). Maternal HCV was associated with a decreased risk of preeclampsia (aRR: 0.39, 95% CI: 0.24–0.64), but an increased risk of preterm birth (aRR: 1.32, 95% CI: 1.08–1.60) and late neonatal death (7–27 days: aRR: 3.79, 95% CI: 1.07–13.39) Preterm birth were also more common in mothers with HBV, aRR: 1.21 (95% CI: 1.02–1.45). Both HBV and HCV are risk factors for preterm birth, while HCV seems to be associated with a decreased risk for preeclampsia. Future studies should corroborate these findings.     

Neonatal mortality in intensive care units of Central Brazil

OBJECTIVE: To identify potential prognostic factors for neonatal mortality among newborns referred to intensive care units. METHODS: A live-birth cohort study was carried out in Goiania, Central Brazil, from November 1999 to October 2000. Linked birth and infant death certificates were used to ascertain the cohort of live born infants. An additional active surveillance system of neonatal-based mortality was implemented. Exposure variables were collected from birth and death certificates. The outcome was survivors (n=713) and deaths (n=162) in all intensive care units in the study period. Cox's proportional hazards model was applied and a Receiver Operating Characteristic curve was used to compare the performance of statistically significant variables in the multivariable model. Adjusted mortality rates by birth weight and 5-min Apgar score were calculated for each intensive care unit. RESULTS: Low birth weight and 5-min Apgar score remained independently associated to death. Birth weight equal to 2,500 g had 0.71 accuracy (95% CI: 0.65-0.77) for predicting neonatal death (sensitivity =72.2%). A wide variation in the mortality rates was found among intensive care units (9.5-48.1%) and two of them remained with significant high mortality rates even after adjusting for birth weight and 5-min Apgar score. CONCLUSIONS: This study corroborates birth weight as a sensitive screening variable in surveillance programs for neonatal death and also to target intensive care units with high mortality rates for implementing preventive actions and interventions during the delivery period.     

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.     

The effect of maternal smoking during pregnancy on intellectual disabilities among 8-year-old children

Prenatal tobacco smoke exposure has been implicated as a risk factor for cognitive deficits in children. The purpose of this study is to examine the association between prenatal tobacco smoke exposure and diagnosis of intellectual disabilities (ID) among 8-year-old children living in Arkansas, Georgia, North Carolina and Utah. In 2002 and 2004, 965 ID case children were identified through a surveillance network and compared with the population of children born in the surveillance region during the same period ( n  = 104 607). Prenatal tobacco smoke exposure was determined from birth certificates. We estimated the effect of prenatal tobacco smoke exposure (none, <10, 10–19 and ≥20 cigarettes per day) on ID using logistic regression.
Generally, the risk of ID was mildly elevated among children whose mothers smoked ≥20 cigarettes per day during pregnancy [RR 1.34; 95% (confidence interval) CI 0.96, 1.87] after adjustment for maternal education, maternal race, maternal age, marital status, child sex, birth year and study site. However, the effect of exposure to ≥20 cigarettes per day significantly differed for males [RR 1.77, 95% CI 1.20, 2.62] compared with females [RR 0.81, 95% CI 0.44, 1.50]. Supplemental analyses reveal substantial confounding of this relationship by socio-economic indicators. A differential effect of tobacco smoke exposure on the risk of ID is suggested for males and females and deserves further investigation; however, the interpretation is tempered by the potential for residual confounding.     

Reproductive history and mortality in late middle age among Norwegian men and women

There is growing recognition that reproductive patterns may have long-term health implications, although most evidence is restricted to women. The authors used register data to derive fertility histories for all Norwegian men and women born in 1935-1958. Discrete-time hazard modeling was used to analyze later-life mortality by aspects of reproductive history. A total of 63,312 deaths were observed during 14.5 million person-years of follow-up in 1980-2003, when subjects were aged 45-68 years. Models included detailed information on educational qualifications and marital status. Odds of death relative to those for subjects with two children were highest for the childless (women: odds ratio (OR) = 1.50, 95% confidence interval (CI): 1.43, 1.57; men: OR = 1.35, 95% CI: 1.30, 1.40) and next highest for those with only one child (women: OR = 1.31, 95% CI: 1.26, 1.37; men: OR = 1.20, 95% CI: 1.16, 1.24). Results for the parous showed a positive association between earlier parenthood and later mortality, a reverse association with late age at last birth, and an overall negative association between higher parity and mortality. The similarity of results for women and men suggests biosocial pathways underlying associations between reproductive history and health. The lack of any high-parity disadvantage suggests that in the "family friendly" Norwegian environment, the health benefits of having several children may outweigh the costs.