Socioeconomic differences in the incidence of small-for-gestational-age birth and their time trend

Abstract

Background: Children born small for gestational age (<10th percentile for birthweight at a particular gestational age; SGA) are at higher risk of morbidity and later disease risk. This study aims to quantify socioeconomic differences in SGA incidence and test whether these inequalities are shifting over time in an English population-based cohort.
Methods: We used 70,818 antenatal care and delivery records of singleton births to mothers aged ≥18 years at University Hospital Southampton, UK, utilising logistic regression modelling to investigate the risk of SGA by maternal educational qualification, employment, partner’s employment status and lone motherhood recorded at the first antenatal appointment. We also adjusted for maternal age, ethnicity, parity, blood pressure, gestational diabetes and baby’s sex. We tested mediation by maternal body mass index (BMI) category and smoking status. Interactions between social indicators and year estimate change in inequality over the study period (2004-2016).
Results: Mothers with no university degree were more likely to give birth to an SGA baby (adjusted odds ratio (aOR) 1.22, 99% CI 1.03, 1.45) than mothers with a degree. Maternal (aOR 1.26, CI 1.09, 1.45) and paternal unemployment (aOR 1.29, CI 1.03, 1.61) were also associated with higher SGA risk compared to employed mothers and partners respectively. There was no evidence of mediation by maternal smoking or BMI for those associations. However, despite lone motherhood being associated with higher risk of SGA (aOR 1.27, CI 1.01, 1.59), this was attenuated by adding maternal smoking status in the model (aOR 1.15, CI 0.92, 1.45). All of the linear trends in ORs by year showed no evidence of narrowing inequalities over time at the 1% statistical significance level.
Conclusion: Social inequalities in SGA incidence are evident, and have remained stable over the 12-year study period. Pre-conception and antenatal interventions targeting socially disadvantaged mothers are needed.

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Identifiers

ORCID for Sam Wilding: orcid.org/0000-0003-4184-2821

ORCID for Paul Roderick: orcid.org/0000-0001-9475-6850

ORCID for Nisreen A. Alwan: orcid.org/0000-0002-4134-8463

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