Four key factors have been identified that together account for more than one-third of the inequalities in infant deaths between the most and least deprived areas of England.

Researchers say targeted interventions to address these factors – teenage pregnancy, maternal depression, preterm birth and smoking during pregnancy – could go a significant way to reduce inequalities, although higher-level structural changes to address socioeconomic inequality will also be necessary.

The UK currently ranks 10th out of 38 OECD countries for infant mortality (deaths in children under the age of one), with four deaths recorded per 1,000 live births.

Children born to mothers who are poor, black or young are known to be at increased risk, but where children are born also matters: according to ONS data for 2022, the mortality rate for infants in the most deprived 10% of England was almost three times higher than for infants living in the least deprived 10%.

“The inequality in infant mortality is at an alarming level,” said Dr Frederick Ho at the University of Glasgow’s School of Health, who led the study. “We also know that infant mortality is an indicator of more general effectiveness in the healthcare system. We wanted to understand the reasons for this inequality, as this could have policy implications for whether we could use the healthcare system to reduce or to eliminate it.”

To investigate, Ho and his colleagues examined 392,606 linked mother and infant health records collected across England between 2004 and 2019, looking at how 24 different social and biological factors may have contributed to infant deaths during this time.

The study, published in The Lancet Regional Health Europe, found that infants in the most deprived areas had double the mortality rate of those in the least deprived areas during the study period, and identified four factors – preterm birth, smoking during pregnancy, teenage pregnancy, and maternal depression – which collectively accounted for 38% of this inequality.

While smoking and maternal depression may affect the biological development of infants, with downstream implications for their health, the association with teenage pregnancy may relate more to circumstances such as reduced access to pre- and postnatal care, or access to fewer financial resources, Ho said.

His data suggests that interventions designed to target these factors – such as screening for depression in early pregnancy, improving GP outreach services to teenage mums, or ongoing efforts to phase out smoking – could help to reduce inequality.

However, Ho added that “even if we have perfect interventions for these factors, we could only reduce the inequality by about a third. This means we also need structural changes targeting socioeconomic inequality if we are going to reduce it in a meaningful way.”

Prof Karen Luyt, a neonatologist at the University of Bristol and director of the National Child Mortality Database (NCMD), said that while this was an important study of deaths preceding the Covid-19 pandemic, it probably underestimated the current impact of deprivation on infant survival.

She said: “The recent NCMD infant mortality data for England from April 2019 to March 2023 highlighted widening social disparities in infant mortality, with a rising year-on-year rate in the most deprived quintile in stark contrast with a stable infant mortality rate in the least deprived quintile.

“[The study] also confirms the causal link between social deprivation and infant mortality as a consequence of premature birth, and estimates that around 15% of infant deaths caused by deprivation are attributable to being born preterm.

“With targeted investment in the provision of equitable access to [evidence-based healthcare interventions] it is possible to prevent preterm birth and to improve survival for babies where preterm birth is inevitable.”

Alex Kennedy, policy and engagement manager at the Health Foundation, a UK health charity and thinktank, said: “For the new government to meet its goal of halving the difference in healthy life expectancy between regions, there must be an explicit focus on children’s health and reducing infant mortality. A key part of this is focusing on reducing deprivation and ensuring communities have access to the building blocks of health – including education, employment and decent housing.”