Adverse pregnancy outcomes linked to socioeconomic and ethnic inequalities

A cohort study published in The Lancet sought to quantify the impact of socioeconomic and ethnic inequalities at the population level in England.¹ Researchers used data compiled by the National Maternity and Perinatal Audit based on birth records from maternity information systems of 132 National Health Service hospitals. Women with singleton pregnancies, and a recorded gestation between 24 and 42 weeks, were included, while women with terminations of pregnancy were excluded.

Researchers analyzed data on stillbirth, preterm birth—defined as 37 weeks or less gestation—and fetal growth restriction (FGR) as liveborn with birth weight less than the third centile per the UK definition.

The study included data from 1,155,981 women with a single birth between April 1, 2015, and March 31, 2017.

The data was compared by socioeconomic deprivation quintile and ethnic group. Attributable fractions for the entire population and specific groups were calculated and compared with least deprived groups or White women, adjusted and unadjusted for smoking, body-mass index (BMI), and other maternal risk factors.

Of 1,155,981 live births, 6% were preterm births (69,175), and 2% were births with fetal growth restriction (22,679). Stillbirths accounted for 4% of births (4,505). The risk of stillbirth was 0.3% in the least socioeconomically deprived group (p=0.0001), and 0.5% in the most deprived group. In the least deprived group, the risk of preterm birth was 4.9%, which increased by 46.9% in the most deprived group at 7.2% (p=0.0001). Risk of fetal growth restriction was 1.2% in the least deprived group, which doubled to 2.2% in the most deprived group (p=<0.0001).

Risk of adverse pregnancy outcomes varied as follows:

• Risk of stillbirth ranged from 0.3% in White women to 0.7% in Black women (p<0.0001);
• risk of preterm birth was 6% in White women, 6.5% in South Asian women, and 6.6% in Black women (p<0.0001); and
• risk of FGR ranged from 1.4% in White women to 3.5% in South Asian women (p<0.0001).

Nearly 12% of stillbirths (95% CI CI 9·8–13·5), 1.2% of preterm births (0·8–1·6), and 16.9% of FGR (16·1–17·8) could be attributed to ethnic inequality.

Before adjusting, population attributable fractions indicated that 23.6% of stillbirths (95% CI 16.7–29.8), 18.5% of preterm births (16.9-20.2) and 31.1% of births with FGR (28.3-33.8) could be attributed to socioeconomic inequality. However, these fractions were substantially reduced when adjusted for ethnic group, smoking, and BMI—11.6% for stillbirths, 11.9% for preterm births, and 16.4% for births with FGR.

Adjustments for socioeconomic deprivation, smoking, and BMI only had a small effect on the ethnic group attributable fractions (13% for stillbirths, 2.6% for preterm births, and 19.2% for births with FGR). According to researchers, group-specific attributable fractions were especially high in the most socioeconomically deprived South Asian women and Black women for stillbirth (53.5% in South Asian women and 63.7% in Black women) and FGR (71·7% in South Asian women and 55·0% in Black women).

The authors concluded that prevention should target the entire population—as well as specific ethnic groups at high risk of adverse pregnancy outcomes—to address risk factors and wider determinants of health.

Reference

1. Jardine J, Walker K, Gurol-Urganci I, et al. Adverse pregnancy outcomes attributable to socioeconomic and ethnic inequalities in England: a national cohort study. The Lancet. Published online November 2021. doi:10.1016/s0140-6736(21)01595-6