Congenital malformations in the Fylde region of Lancashire, England 1957-1973

Association between social position and congenital anomalies: A population-based study among 19,874 Danish women

Aims: To examine the association between maternal and paternal educational level and household income and the risk of giving birth to a baby with a congenital anomaly in a population of Danish women. Methods: We performed a population-based cohort study, based on record linkage of data from Danish administrative registries. For each pregnant woman in the cohort, we described financial and educational resources and congenital anomalies in her offspring. We used logistic regression to model the association between social position and congenital anomalies. Results: The analyses included all 19,874 primiparous singleton deliveries in North Jutland county, Denmark, from 1991 to 1998. There were 1025 (5.2%) babies with congenital anomalies. The odds ratios (ORs) for giving birth to a baby with a congenital anomaly showed a dose— response decline, as the mothers' educational level increased. Women with less than 10 years of schooling had an almost three-fold increased risk of giving birth to an infant with a congenital anomaly, as compared with women with more than 4 years of higher education (OR=2.9, 95% confidence interval = 1.8—4.6). Paternal educational level and household income were, to a lesser degree, associated with congenital anomalies in the offspring. Conclusions: Maternal educational level, and to a lesser degree paternal educational level and household income, were associated with the risk of giving birth to a baby with a congenital anomaly. However, the analysis did not take into account maternal health status, and the results might be due to differential misclassification or residual confounding.

Socio-economic status and risk of conotruncal heart defects and orofacial clefts

Studies of socio-economic status (SES) have figured prominently in research related to a variety of health outcomes, although the question remains as to whether SES contributes to the aetiologies of congenital anomalies. This study examines the association of SES with risks of conotruncal heart defects and orofacial clefts, using interview data from 696 case mothers (86% of eligible) and 734 (78%) control mothers from a population-based case-control study. Socio-economic measures from maternal interview included mother's education and employment. Reported addresses were linked with the US census to characterise six measures of neighbourhood SES (education, poverty, unemployment, occupation, crowding and rental occupancy). Results were adjusted for race-ethnicity, multivitamin/mineral supplement intake, cigarette smoking and binge drinking. Results for individual and neighbourhood measures suggested that low SES was associated with increased risk of d-transposition of the great arteries (dTGA), reduced risk of tetralogy of Fallot (TOF), but was not associated with risk of orofacial clefts. For example, when examining odds ratios (OR) that compared risks among women whose neighbourhoods were in the lowest vs. highest quartile of the census-based SES measures, ORs for five of the six measures were> 1.4 for dTGA, and ORs for all six measures were < 0.7 for TOF. ORs for clefts tended to be closer to 1. This study suggests that SES risks are birth defect specific.

Socioeconomic status, neighborhood social conditions, and neural tube defects

OBJECTIVES

This study evaluated the contributions of lower socioeconomic status (SES) and neighborhood socioeconomic characteristics to neural tube defect etiology. The influence of additional factors, including periconceptional multivitamin use and race/ethnicity, was also explored.

METHODS

Data derived from a case-control study of California pregnancies from 1989 to 1991. Mothers of 538 (87.8% of eligible) case infants/fetuses with neural tube defects and mothers of 539 (88.2%) nonmalformed infants were interviewed about their SES. Reported addresses were linked to 1990 US census information to characterize neighborhoods.

RESULTS

Twofold elevated risks were observed for several SES indicators. Risks were somewhat confounded by vitamin use, race/ethnicity, age, body mass index, and fever but remained elevated after adjustment. A risk gradient was seen with increasing number of lower SES indicators. Women with 1 to 3 and 4 to 6 lower SES indicators had adjusted odds ratios of 1.6 (1.1-2.2) and 3.2 (1.9-5.4), respectively, compared with women with no lower SES indicators.

CONCLUSIONS

Both lower SES and residence in a SES-lower neighborhood increased the risk of an neural tube defect-affected pregnancy, with risks increasing across a gradient of SES indicators.

An entropy-based algorithm for detecting clusters of cases and controls and its comparison with a method using nearest neighbours

A new method for detecting disease clustering based on entropy is presented. For this method cases and controls are plotted on a map. The map is divided into regions. The entropy of the space is calculated as the log of the number of possible ways of placing the cases and controls in the various regions given the total number of cases and controls and the number of cases and controls in each region. The power of the entropy technique is tested against the power of the nearest neighbour technique (NNT). The entropy method is shown to be substantially more powerful than the NNT when there is more than one cluster in the space or when the clusters are near the boundary of the space.

Involvement of deprivation and environmental lead in neural tube defects: a matched case-control study

OBJECTIVE

To analyse the prevalence of neural tube defects in small geographical areas and seek to explain any spatial variations with reference to environmental lead and deprivation.

SETTING

The Fylde of Lancashire in the north west of England.

DESIGN

Cases were ascertained as part of a prospective survey of major congenital malformations in babies born in the Fylde to residents there between 1957 and 1981. A matched case-control analysis used infants with cardiovascular system, alimentary tract, and urinary system malformations as controls. Conditional logistic regression was used to assess the effects of more than 10 micrograms/l lead in drinking water and the Townsend deprivation score.

RESULTS

The prevalence of neural tube defects in 1957-73 was higher in Blackpool, Fleetwood, and North Fylde, whereas the three control groups showed no significant spatial variation. In 1957-81 mothers living in electoral wards with either a higher proportion of houses with more than 10 micrograms/l lead in the water or a higher deprivation score had a greater risk of having a baby with a neural tube defect. For spina bifida and cranium bifidum alone, this was also true. For anencephaly, deprivation was less important although the effect of lead was still seen. In some neural tube defects, lead may act independently of other possible factors associated with deprivation. It seemed unlikely that lead levels changed significantly during the survey. The percentage of houses with 10 micrograms/l or more of lead in the water in 1984-5 was similar to that found in Great Britain 10 years previously.

CONCLUSION

There is evidence to suggest that lead is one cause of neural tube defects, especially anencephaly. This could link the known preventive actions of hard water and folic acid. Calcium is a toxicological antagonist of lead. One cause of a deficiency of folic acid is impaired absorption secondary to zinc deficiency, which may be produced or exacerbated by lead.