Short, Black, Baird, Himsworth, and social class differences in fetal and neonatal mortality rates

An exploratory spatial analysis to assess the relationship between deprivation, noise and infant mortality: an ecological study

BACKGROUND

Few studies have explored how noise might contribute to social health inequalities, and even fewer have considered infant mortality or its risk factors as the health event of interest.In this paper, we investigate the impact of neighbourhood characteristics - both socio-economic status and ambient noise levels - on the spatial distribution of infant mortality in the Lyon metropolitan area, in France.

METHODS

All infant deaths (n = 715) occurring between 2000 and 2009 were geocoded at census block level. Each census block was assigned multi-component socio-economic characteristics and Lden levels, which measure exposure to noise. Using a spatial-scan statistic, we examined whether there were significant clusters of high risk of infant mortality according to neighbourhood characteristics.

RESULTS

Our results highlight the fact that infant mortality is non-randomly distributed spatially, with clusters of high risk in the south-east of the Lyon metropolitan area (RR = 1.44; p = 0.09). After adjustments for socio-economic characteristics and noise levels, this cluster disappears or shifts according to in line with different scenarios, suggesting that noise and socio-economic characteristics can partially explain the spatial distribution of infant mortality.

CONCLUSION

Our findings show that noise does have an impact on the spatial distribution of mortality after adjustments for socio-economic characteristics. A link between noise and infant mortality seems plausible in view of the three hypothetical, non-exclusive, pathways we propose in our conceptual framework: (i) a psychological pathway, (ii) a physiological disruption process and (iii) an unhealthy behaviours pathway. The lack of studies makes it is difficult to compare our findings with others. They require further research for confirmation and interpretation.

Contribution of smoking during pregnancy to inequalities in stillbirth and infant death in Scotland 1994-2003: retrospective population based study using hospital maternity records

OBJECTIVE

To quantify the contribution of smoking during pregnancy to social inequalities in stillbirth and infant death.

DESIGN

Population based retrospective cohort study.

SETTING

Scottish hospitals between 1994 and 2003.

PARTICIPANTS

Records of 529 317 singleton live births and 2699 stillbirths delivered at 24-44 weeks' gestation in Scotland from 1994 to 2003.

MAIN OUTCOME MEASURES

Rates of stillbirth and infant, neonatal, and post-neonatal death for each deprivation category (fifths of postcode sector Carstairs-Morris scores); contribution of smoking during pregnancy ("no," "yes," or "not known") in explaining social inequalities in these outcomes.

RESULTS

The stillbirth rate increased from 3.8 per 1000 in the least deprived group to 5.9 per 1000 in the most deprived group. For infant deaths, the rate increased from 3.2 per 1000 in the least deprived group to 5.4 per 1000 in the most deprived group. Stillbirths were 56% more likely (odds ratio 1.56, 95% confidence interval 1.38 to 1.77) and infant deaths were 72% more likely (1.72, 1.50 to 1.97) in the most deprived compared with the least deprived category. Smoking during pregnancy accounted for 38% of the inequality in stillbirths and 31% of the inequality in infant deaths.

CONCLUSIONS

Both tackling smoking during pregnancy and reducing infants' exposure to tobacco smoke in the postnatal environment may help to reduce stillbirths and infant deaths overall and to reduce the socioeconomic inequalities in stillbirths and infant deaths perhaps by as much as 30-40%. However, action on smoking on its own is unlikely to be sufficient and other measures to improve the social circumstances, social support, and health of mothers and infants are needed.

Social class and census-based deprivation scores: which is the best predictor of stillbirth rates?

This study investigates whether social class or a census-based deprivation score is a better predictor of stillbirth rates using data for 1993-5 for residents of South Thames (West) Region. Social class is routinely coded for 10% of live births and 100% of stillbirths. A Townsend deprivation score was assigned to each stillbirth and each live birth with a social class code, according to their electoral ward of residence. In unifactorial analyses of stillbirth rate the relationship was stronger with social class (P = 0.008) than with Townsend score (P = 0.11). Both relationships were strengthened by including those births recorded as social class 'other' ['other' vs. social class I odds ratio (OR) = 2.27, P < 0.001; lower vs. upper septile deprivation score OR = 1.45, P = 0.07)]. When social class and Townsend score were analysed together, the ORs for social class remained similar to before, but the Townsend ORs were reduced and non-significant overall. We conclude that social class, which is based on data on each individual, is a better predictor of stillbirth than Townsend score, which is based on data from the area of residence. We recommend further investigation of the stillbirth risk in the subgroups that make up the 'other' social class.

Perinatal death: worse obstetric and neonatal outcome in a subsequent pregnancy

A retrospective case-control study was undertaken of women with a history of a previous stillbirth or neonatal death, who subsequently delivered in BMH Rinteln. Their obstetric and neonatal outcome was compared to that of a control group of women of similar age and parity and its relationship to specific socio-economic factors assessed. Index patients had a worse obstetric and neonatal outcome. They were statistically significantly more likely to be admitted to hospital during their pregnancy (46% vs 26%), to have medical complications (58% vs 34%), to be delivered prematurely (16% vs 8%), and by Caesarean section (22% vs 9%). Their babies were more likely to have complications (28.8% vs 20.4%), to be of low birth weight (14% vs 7%), require intubation (11% vs 5%) and be admitted to the Special Care Baby Unit (SCBU) (13% vs 7%). Apart from small stature, no differences in socio-economic factors between the two groups could be identified. Index patients were four times more likely than controls to have their pregnancy terminated prematurely as a result of complications (6.7% vs 1.6%), but there was also a high level of obstetric intervention in the absence of clear medical indications. Although perinatal mortality was not statistically increased, the results were suspicious and it is concluded that these women should continue to be considered a high-risk group.

Stillbirth rate and associated risk factors among 869 750 Latin American hospital births 1982-1986

Fetal death is essential to evaluate perinatal outcome. Accurate stillbirth rate however is difficult to obtain; this is especially so in developing countries. Current information was obtained through a clinical-epidemiological study, ECLAMC, during the 1982-1986 period for a total sample of 869 750 births in 102 hospitals belonging to 11 Latin American countries. The overall stillbirth rate was 2.0%, the highest being in Bolivian (4.4%) and the lowest in Chilean hospitals (0.9%). In all countries there was a high mortality rate among male fetuses. The incidence of stillbirth in multiple pregnancies almost doubled that for singletons. A steady increase with increasing maternal age was observed. The proportion of all births in mothers 35 years of age or older was 10.1%, while the stillbirth proportion among all stillbirths in the same maternal age group was 18.8%. As expected, a higher fetal mortality rate (10.7%) was found in the low birthweight group (less than or equal to 2500 g) than in the group with birthweight greater than 2500 g (0.6%). One out of ten births occurred in the former group. A striking difference was observed in the stillbirth rate between hospitals with free obstetrical care (2.5%) and those in which any type of payment was required (1.4%). Although socioeconomical factors are probably the main factors responsible for fetal death, increased maternal age and a high incidence of low birthweight also contributed greatly to fetal mortality. These risk factors for fetal mortality should be the target of public health actions in these countries.

The work of the National Perinatal Epidemiology Unit. One example of technology assessment in perinatal care

This article describes one approach to assessing the effects of perinatal care--that adopted by the National Perinatal Epidemiology Unit in Oxford, England. The unit's research has been based primarily on a combination of simple, descriptive analyses of observational data and statistically robust analyses of evidence derived from randomized controlled trials.

'Normal but dead': perinatal mortality in non-malformed babies of birthweight 2.5 kg and over in the northern region in 1983

The case notes relating to 75 of the 91 perinatal deaths of nonmalformed babies of birthweight greater than or equal to 2.5 kg born in the Northern Region in 1983 were examined. The major groups involved antepartum deaths of unknown cause (40%), and deaths due to intrapartum anoxia or trauma (35%). A case-control study compared each of the 75 cases with two controls matched for place of birth, obtained by taking the next two babies born in the same maternity unit (excluding perinatal deaths, birthweight less than 2.5 kg, and malformations). Four factors were found to be significantly associated with risk of perinatal death in this group: primigravidity, parity greater than or equal to 3, not booked for antenatal care by 20 weeks, and corrected birthweight less than 3.2 kg (adjusted for gestation). Two further factors were related only to the risk of perinatal death consequent upon intrapartum events: labour post-term and malpresentation in labour. All four factors relevant to the whole group remained independently associated with risk of perinatal death after multivariate analysis by two techniques. Adjusted odds ratios (95% CI) were estimated as: primigravidity 2.1 (1.1 to 4.1); parity three or more 5.7 (1.9 to 17); not booked for antenatal care by 20 weeks 15.7 (3.0 to 81); and corrected birthweight less than 3.25 kg 2.5 (1.3 to 4.6). An avoidable factor, as defined, was detected in 50% of deaths. In 30% of deaths there was an avoidable factor (grade 2) such that absence may have been expected to lead to a different outcome had all other factors remained equal. Of the avoidable factors detected, 61% related to intrapartum management, as did 76% of the grade 2 factors. Most of these involved failure to respond to evidence of fetal distress in labour. The defined group constituted 21% of all perinatal deaths, suggesting that this is an important category, particularly as their potential for normal survival should otherwise have been high.

[Social differences in the prenatal and postnatal mortality: Switzerland 1979-1985]

The influence of social factors on birthweight and fetal and infant mortality was investigated in the Swiss birth cohort from 1979-85 (N = 519,933). The proportion of newborns with low-birthweight (less than 2500 g) was higher in lower social classes. Stillbirth-rate, neonatal and postneonatal mortality were higher in lower social classes, too. When controlling for birthweight, the increase in mortality in the lower social classes became somewhat less striking. Marked social differences in perinatal mortality were found in the newborns with normal weight, whereas almost no difference could be detected in the low-birthweight-group.

Identification of high risk and low risk

Identification of high risk is only moderately successful at the booking visit; most risk factors only give a relative risk of around three, so that most of the high-risk group do not experience the adverse outcome, and most adverse outcomes occur in low-risk women. Risk factors are useful in planning for confinement and extra care, but since new problems can arise at any time and most antenatal admissions are for conditions arising in spite of antenatal care (Chng et al, 1980), some care should be offered to all women. Traditional schedules of care, however, have no scientific justification. Identification of low risk is also fallible and there seems to be an irreducible minimum of unpredictable problems which will arise even in low-risk women. Methods need to be found to reduce the lack of continuity which often results from unscheduled transfers of care.

Perinatal mortality in Northern Ireland: where are we now?

Perinatal mortality in Northern Ireland has been declining over the last 30 years, but the factors which may account for this fall have not been clearly delineated. Crude perinatal mortality figures yield very little insight into the problem, and meaningful management statistics are urgently required if service performance is to be reasonably assessed. This paper sets out the case for birth-weight standardisation and explores the utility of a broad diagnostic taxonomy of causes of death.

Social class differences in infant mortality: the problem of competing hypotheses

There is no agreed explanation of the social class gradient in infant mortality. The longstanding debate continues between those who favour explanations based on natural or social selection and those who stress the influence of environmental circumstances. These explanations are often presented as competing hypotheses between which it is necessary to make an absolute choice. An article which takes this approach is critically examined. It is argued that such an approach may lead to erroneous conclusions, and may divert attention away from the primary task of understanding how to bring about further improvements in the survival of infants in the manual social classes.

The health of children of low-income families

Childhood poverty is common in Canada: 1,114,000 children under 16 years of age live below the poverty line. The incidence is highest among children of single mothers, unemployed parents, Canadian native peoples and recent immigrants, particularly refugees. Compared with the national average, the infant mortality rate is twice as high, deaths from infectious diseases are 2.5 times more common and accidental deaths are twice as common among children of low-income families. Other problems associated with poverty are iron deficiency anemia, dental caries, chronic ear infections, mental retardation, learning disabilities, poor school performance and increased suicide rates. Health care professionals can help address the poor physical and mental health associated with poverty in children by promoting a broad range of public policies.

Maternal smoking and low birthweight: implications for antenatal care

The incidence of low birthweight has been related to smoking prevalence in each social group using published data for 1984. The attributable risk of low birthweight has been estimated, based on a relative risk of 2 for mothers who smoke during pregnancy. Assuming 12.5% of cigarette smokers stopped smoking during pregnancy, 18.1% of all low weight births were caused by maternal smoking in 1984. The percentage for most social groups was similar. The overall attributable risk from smoking was estimated to be 12.7 low weight births per 1000 total births, with a further 12.1 per 1000 due to other factors acting in a socioeconomic gradient. We estimate that the minimum attainable low birthweight incidence in 1984 was 45.4 per 1000 total births, based on the lowest observed incidence, corrected for smoking prevalence, which was in social group II. We recommend the addition of maternal smoking information to the Korner maternity clinical options data set, to enable an accurate assessment of the risks and to provide local monitoring of initiatives to reduce smoking prevalence during pregnancy.