Explanations for social inequalities in preterm delivery in the prospective Lifeways cohort in the Republic of Ireland

Abstract

Background: Social inequalities in pregnancy outcomes have been extensively described but studies that explain these inequalities comprehensively are lacking. This analysis evaluated the contribution of material, psychosocial, behavioural, nutritional and obstetrical factors in explaining social inequalities in preterm delivery.

Methods: The data were based on a prospective cohort of 1109 Irish pregnant women. Preterm delivery was obtained from clinical hospital records. Socio-economic status was measured using educational level. The contribution of the above factors in explaining the association between educational level and preterm delivery was examined using Cox models.

Results: Educational level was found to be a significant predictive factor of preterm delivery; women with low educational level were more likely to have a preterm delivery [hazard ratio (HR) = 2.14, 95% confidence interval (95% CI): 1.04-4.38)] after adjustment for age and parity. Rented and crowded home, smoking, alcohol consumption and intake of saturated fatty acids displayed educational differences and were predictive of preterm delivery. Material factors (rented and crowded home) reduced the HR of preterm delivery for low compared with highest educated women by 33%. The additional independent contribution of behavioural factors (smoking and alcohol consumption) was 5% and of saturated fatty acids intake was 4%. All these factors combined reduced the HR of preterm delivery for low educated women by 42% (HR = 1.66, 95% CI: 0.76-3.63).

Conclusion: This study underlines the importance of material, behavioural and nutritional factors in explaining social inequalities in preterm delivery. These findings have cross-sectoral public policy implications.