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Study of over a million births finds stark inequalities in pregnancy outcomes

Published: 02 November 2021

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A nationwide study of over 1 million births (over 94% of all births) in the English National Health Service (NHS) between 2015 and 2017, co-authored by Professor Asma Khalil from St George’s, University of London, has found extreme inequalities in pregnancy outcomes between different ethnic and socioeconomic groups in England.

Published in The Lancet, the findings suggest that current national programmes to make pregnancy safer, which focus on individual women’s choices and behaviour and their antenatal care, will not be enough to improve outcomes for babies born in England. The authors say that to reduce disparities in birth outcomes at a national level, politicians and healthcare providers must work together to address racism and discrimination and to improve social circumstances, social support, and the health of women throughout their lives.

The NHS has set a target of halving rates of stillbirth and neonatal death, and reducing levels of preterm birth by 25%, by 2025. Socioeconomic deprivation and minority ethnic background are known risk factors for adverse pregnancy outcomes. However, little is known about the strength of these risk factors or the scale of their impact at the population level.

To find out more, researchers analysed NHS hospital data linked to the National Maternity and Perinatal Audit between 1st April 2015 and 31st March 2017, to quantify the impact of socioeconomic and ethnic inequalities on stillbirth (the death of a fetus after 24 weeks of pregnancy), preterm birth (livebirth before 37 weeks’ gestation), and low birthweight in England.

The researchers calculated the proportion of adverse pregnancy outcomes that would not have occurred if all women had the same pregnancy risk as women in the least deprived socioeconomic group or as those from a white ethnic background, both with and without adjusting for smoking status and body mass index (BMI) at the beginning of pregnancy. Socioeconomic status was measured for each area using the Index of Multiple Deprivation that combines information on income, employment, education, housing, crime and the living environment.

In total, 1,155,981 women with a singleton birth were included in the study, of whom 77% were white, 12% South Asian, 5% Black, 2% mixed race/ethnicity, and 4% other race/ethnicity. Overall, 4,505 women had a stillbirth (0.4%). Of the 1,151,476 liveborn babies, 69,175 (6%) were preterm births and 22,679 (2%) births with low birthweight (table 1).

The analysis estimates that 24% of stillbirths, 19% of live preterm births and 31% of livebirths with low birthweight would not have occurred if all women had the same risk of adverse pregnancy outcomes as women in the most affluent socioeconomic group (table 2). However, adjusting for ethnicity, maternal smoking and BMI substantially reduced these inequalities (12%, 12%, and 16%, respectively)—suggesting that a considerable part of the socioeconomic inequalities in pregnancy outcomes can be explained by these maternal characteristics.

Pregnancy complications were found to disproportionately affect Black and minority ethnic women—with 12% of stillbirths, 1% of preterm births and 17% of births with low birthweight attributed to ethnic inequality. Importantly, adjusting for socioeconomic deprivation, maternal smoking and BMI had little impact on these outcomes—indicating that other factors related to ethnicity and culture may contribute to poor pregnancy outcomes.

However, the largest increases in excess risk of stillbirth and low birthweight occurred in the most socioeconomically disadvantaged South Asian and Black women. For example, more than half of stillbirths and three quarters of births with low birthweight among the most deprived South Asian women were attributable to socioeconomic and ethnic inequalities, and were therefore avoidable.

Professor Khalil from the Molecular and Clinical Sciences Research Institute at St George’s and co-lead author on the paper, said: “We need concerted action to address this disparity in pregnancy outcomes.

“We require midwives, obstetricians, clinicians and policymakers to come together to do more to prevent adverse pregnancy outcomes in at-risk groups. Interventions that target smoking and obesity work, and in turn could have a significant impact on reducing complications at birth. At the same time, we need to acknowledge systemic issues that affect black and ethnic minority women and take action to make sure they are not left behind.”

The authors propose three measures to reduce inequalities in pregnancy outcomes, including targeting high-risk groups with clinical interventions during pregnancy, developing programmes to help stop smoking and promote healthy diets, as well as improving access to high-quality antenatal care (for example, by monitoring of fetal growth more precisely and frequently and offering to induce labour when stillbirth risk is increased). They also recommend public health strategies to reduce inequalities in women’s health before pregnancy, focusing on smoking and dietary habits as well as wider aspects of maternal adversity, such as mental health issues, substance abuse, and stress related to social disadvantage. Lastly, they call for wider policies to address the key causes of inequality, such as income, education, and employment, that indirectly influence pregnancy outcomes.

Dr Jennifer Jardine, co-lead author from the Royal College of Obstetrics and Gynaecologists, UK, said: “The stark reality is that across England, women’s socioeconomic and ethnic background are still strongly related to their likelihood of experiencing complications during pregnancy. I think people will be shocked to learn how many mothers and babies in England are affected.

“Over the past few decades, efforts to close the gap in birth outcomes focusing primarily on improving antenatal care and targeting individual behaviours have not been successful. Birth outcomes are not just the end product of pregnancy but the entire life of the mother. While we must continue to encourage healthy behaviours during pregnancy, we also need public health professionals and politicians to strengthen efforts to address the lifelong, cumulative impact of racism and social and economic inequalities on the health of Black and ethnic minority women, families, and communities.”

The authors acknowledge that their findings show observational differences and note some methodological limitations, including that they used an area-based measure of socioeconomic deprivation which might not accurately represent the range of individuals’ socioeconomic status within a particular area; and that their findings assume that the effects of socioeconomic deprivation and ethnicity are not modified by other circumstances, such as overall health, lifestyle, and nutrition—which may limit the conclusions that can be drawn.

Professor Jan van der Meulen, co-lead author from the London School of Hygiene and Tropical Medicine, said: “There are many possible reasons for these disparities. Women from deprived areas and Black and minority ethnic groups may be at a disadvantage because of their environment (for example, because of pollution, poor housing, social isolation, poor access to maternity and health care, insecure employment, more stressful life events), as well as factors that negatively affect their health such as smoking and mental illness.

“National programmes to make pregnancy safer will only be realistically achieved through concerted effort by public health professionals and politicians to tackle the broader socioeconomic and ethnic inequalities.”

The study was funded by the Healthcare Quality Improvement Partnership. It was conducted by researchers from The Royal College of Obstetricians and Gynaecologists, UK; St George's, University of London; London School of Hygiene and Tropical Medicine; Royal Free London NHS Foundation Trust, UK; St George’s Hospital; De Montfort University, London.

St George’s heads up a diverse programme of pregnancy-related research. The university is currently leading on a clinical trial to assess the optimal dose interval for Covid-19 vaccination for pregnant women. You can find out more about the trial in our news story here.

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