Jardine, J. et al | 2021 | Adverse pregnancy outcomes attributable to socioeconomic and ethnic inequalities in England: a national cohort study | The Lancet | DOI: https://doi.org/10.1016/S0140-6736(21)01595-6

The authors of this national cohort study set out to quantify socioeconomic and ethnic inequalities in stillbirth, preterm birth, and FGR in England, taking account of health at the onset of pregnancy and complications that arise during pregnancy.

This study of more than 1 million births in the English National Health Service found that a substantial proportion of stillbirths, preterm births, and fetal growth restriction would not have occurred if all women had the same risk as women in the least deprived socioeconomic group and women from White ethnic groups. The largest increases in the risk of stillbirth and fetal growth restriction occurred in Black and South Asian women. These results show that initiatives to reduce adverse birth outcomes focusing on individual women's choices and behaviour and on antenatal care will have limited effects.

Summary

Background

Socioeconomic deprivation and minority ethnic background are risk factors for adverse pregnancy outcomes. We aimed to quantify the magnitude of these socioeconomic and ethnic inequalities at the population level in England.

Methods

In this cohort study, we used data compiled by the National Maternity and Perinatal Audit, based on birth records from maternity information systems used by 132 National Health Service hospitals in England, linked to administrative hospital data. We included women who gave birth to a singleton baby with a recorded gestation between 24 and 42 completed weeks. Terminations of pregnancy were excluded. We analysed data on stillbirth, preterm birth (<37 weeks of gestation), and fetal growth restriction (FGR; liveborn with birthweight <3rd centile by the UK definition) in England, and compared these outcomes by socioeconomic deprivation quintile and ethnic group. We calculated attributable fractions for the entire population and specific groups compared with least deprived groups or White women, both unadjusted and with adjustment for smoking, body-mass index (BMI), and other maternal risk factors.

Findings

We identified 1 233 184 women with a singleton birth between April 1, 2015, and March 31, 2017, of whom 1 155 981 women were eligible and included in the analysis. 4505 (0·4 per cent) of 1 155 981 births were stillbirths. Of 1 151 476 livebirths, 69 175 (6·0 per cent) were preterm births and 22 679 (2·0 per cent) were births with FGR. Risk of stillbirth was 0·3 per cent in the least socioeconomically deprived group and 0·5 per cent in the most deprived group (p less than 0·0001), risk of a preterm birth was 4·9 per cent in the least deprived group and 7·2 per cent in the most deprived group (p less than 0·0001), and risk of FGR was 1·2 per cent in the least deprived group and 2·2 per cent in the most deprived group (p less than 0·0001). Population attributable fractions indicated that 23·6 per cent (95 per cent CI 16·7–29·8) of stillbirths, 18·5 per cent (16·9–20·2) of preterm births, and 31·1 per cent (28·3–33·8) of births with FGR could be attributed to socioeconomic inequality, and these fractions were substantially reduced when adjusted for ethnic group, smoking, and BMI (11·6 per cent for stillbirths, 11·9 per cent for preterm births, and 16·4 per cent for births with FGR). Risk of stillbirth ranged from 0·3 per cent in White women to 0·7 per cent in Black women (p less than 0·0001); risk of preterm birth was 6·0 per cent in White women, 6·5 per cent in South Asian women, and 6·6 per cent in Black women (p less than 0·0001); and risk of FGR ranged from 1·4 per cent in White women to 3·5 per cent in South Asian women (p less than 0·0001). 11·7 per cent of stillbirths (95 per cent CI 9·8–13·5), 1·2 per cent of preterm births (0·8–1·6), and 16·9 per cent of FGR (16·1–17·8) could be attributed to ethnic inequality. Adjustment for socioeconomic deprivation, smoking, and BMI only had a small effect on these ethnic group attributable fractions (13·0 per cent for stillbirths, 2·6 per cent for preterm births, and 19·2 per cent for births with FGR). Group-specific attributable fractions were especially high in the most socioeconomically deprived South Asian women and Black women for stillbirth (53·5 per cent in South Asian women and 63·7 per cent in Black women) and FGR (71·7 per cent in South Asian women and 55·0 per cent in Black women).

Interpretation

Our results indicate that socioeconomic and ethnic inequalities were responsible for a substantial proportion of stillbirths, preterm births, and births with FGR in England. The largest inequalities were seen in Black and South Asian women in the most socioeconomically deprived quintile. Prevention should target the entire population as well as specific minority ethnic groups at high risk of adverse pregnancy outcomes, to address risk factors and wider determinants of health.

The findings have now been published in the journal The Lancet

Adverse pregnancy outcomes attributable to socioeconomic and ethnic inequalities in England: a national cohort study [paper]

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