The contrast is as stark as ever: one in seven children who live with a single, poorly-educated, unemployed mother end up in care before their seventh birthday. For children who live with both their parents and whose mothers stayed in education beyond secondary school and have never needed social assistance, the figure is fewer than one in 2,000.

The statistics come from a Swedish epidemiological study of children in out-of-home care. The largest of its kind, it involved 14,839 children and young people with experience of having been in care – and more than a million never cared for away from home.

Writing in the British Journal of Social Work, investigators Eva Franzén, Bo Vinnerljung and Anders Hjern claim that the findings add up to compelling argument for social policies that “systematically offer the children of single mothers on long-term social assistance access to evidence-based prevention programs”.

The conviction echoes similar UK work conducted by Andrew Bebbington and John Miles nearly twenty years ago, when a large epidemiological study revealed that having a lone parent was the single strongest risk factor for care placement. The Swedish study represents a rare attempt to replicate and expand Bebbington and Miles’s work.

Franzén’s team made use of Sweden’s national registers of socio-economic and health indicators. Every resident from birth or date of immigration into the country can be tracked through both registers by keying their ten-digit PIN. Identifying first placement in out-of-home care as an outcome, information was also gathered on the socio-economic characteristics of mothers.

For example, information about maternal household status (i.e. single/ married/co-habiting) and maternal income was obtained from the the Total Income Enumeration Register; maternal education data were assembled from the Register of Education, and so on.

Associations between findings on all these fronts were examined separately in relation to infants (0-6 years), pre-teens (7-12 years) and adolescents (13-16 years).

The same pattern emerged across all three: the children of single status, low-educated and unemployed mothers were much more likely to enter out-of-home care before the age of seven.

Children whose mother or father was admitted to hospital because of a suicide attempt, addiction problem or psychiatric disorder were also at high risk.

In cases where these two factors coincided the risk was very high. Weaker associations were found for low maternal income, teenage motherhood and second-generation immigrant children.

The trend was less marked among adolescents, but significant nonetheless. Those placed in care so late were more likely to be admitted because of behavioral problems – a risk factor not usually related to socio-economic status. The common reason for children in the lower age ranges was neglect - a condition solidly linked to socio-economics. So it is perhaps not surprising that the trend was slightly weaker for the adolescent group.

Franzén cautions that the Swedish study examined only the associations between particular variables; it did not try to pinpoint or to take into consideration any chains of effect. For example, poor maternal education might mediate maternal unemployment – but such possibilities were not pursued. In order to tackle them, Franzén notes, data even more precise than Swedish bureaucracy can provide would be needed.

[For a link to Bebbington and Miles’s findings see: The Background of Children who enter Local Authority Care]

• Summary of Franzén E, Vinnerljung B and Hjern A “The Epidemiology of Out-of-Home Care for Children and Youth: A National Cohort Study”, British Journal of Social Work, 38, (6), pp.1043 -1059.