By Kristian Dye
This week I’m looking at two very sad cases of stillbirth in Cali, Colombia.
When we think of disease caused by social circumstance we often imagine non-communicable diseases or infectious diseases, usually where poor living conditions loom large in the aetiology.
When we consider the higher rates of genetic birth defects in socially disadvantaged populations we often express our dismay at what rotten luck it is that this happens to people who are also poor. Here, we miss a key to understanding these diseases. The circumstance of being socioeconomically deprived can provide the conditions necessary for defects of the type in these cases to occur.
Sirenomelia is a rare congenital defect with a prevalence rate of around 1 in every 100,000 birth, and 300 cases have been reported in the literature. The aetiology and pathophysiology of the defect is not well understood, but is thought to be related to vascular abnormality.
‘The vascular steal hypothesis suggests the existence of an anomalous vessel impeding proper blood flow to the caudal end of the embryo. One of the most important early findings in prenatal imaging is a SUA [single uterine artery] of abnormal origin, with SUA of vitelline origin being considered characteristic of sirenomelia.’
There are a number of known risk factors associated with sirenomelia, including maternal diabetes and exposure to teratogenic drugs (such as anti-convulsants or retinoids). Neither mother had abnormal glycaemic control, and neither had been exposed knowingly to teratogens. Incidence of sirenomelia appears to decrease with advancing maternal age – and both women were in the non-increased prevalence group. The only common risk factor between the women was their access to water. Both women relied upon a nearby river for their water – a river which is known to be contaminated with leachate from landfill.
‘During their normal daily activities they were exposed to the river that flows near their homes, where they would wash their clothes and perform personal hygiene activities.’
The contaminated water is known to affect changes in the fish population. The women lived less than 2km from one another. There is a large amount of literature which has observed a correlation between socio-economic status and increased incidence of congenital abnormality – and in particular between proximity to landfill and deformity. One study, of centers in the UK, found that the relative risk of non-chromosomal abnormalities increased by 40% between the most affluent quintile and the most deprived. Where the literature perhaps underestimates the effect at the level of the global population is that the majority of studies are based in the North America or Europe, where socioeconomic deprivation is less relative to the global standard, and where there is a great deal more environmental regulation than elsewhere in many other parts of the world.What is clear, however, is that we can’t think of socially determined health in simple terms of diseases that are transmitted within poor conditions, or are developed as a result of poor nutrition, education or living conditions. Children can be born with disability and disease as a result of the conditions their mothers live in.
5. http://www.marchofdimes.org/materials/global-report-on-birth-defects-the-hidden-toll-of-dying-and-disabled-children-full-report.pdf Page 23