Abstract

OBJECTIVE: To describe the extent of socioeconomic inequalities in low birth weight. To assess the relative benefits of measuring socioeconomic status by individual occupation, socioeconomic deprivation status of area of residence, or both, for describing inequalities and targeting resources. DESIGN: Analysis of birth registrations by registration status: joint compared with sole registrants ("lone mothers"), routinely recorded parental occupation (father's for joint registrants), and census derived enumeration district (ED) deprivation. SETTING: England and Wales, 1986-92. SUBJECTS: 471,411 births with coded parental occupation (random 10% sample) and birth weight. MAIN OUTCOME MEASURES: Proportion of low birth weight (< 2500 g) RESULTS: 34% of births to joint registrants in social classes IV and V, and 45% of births to sole registrants, were in the quintile of most deprived EDs. It was found that 6.8% of births were of low birth weight. Sole registrants were at higher risk (9.3% overall) than joint registrants, across all deprivation quintiles. For joint registrants, the socioeconomic risk gradient was similar by social class or area deprivation, but a greater gradient from 4.7% to 8.7% was found with combined classification. CONCLUSIONS: Up to 30% of low birth weight can be seen as being associated with levels of socioeconomic deprivation below that of the most affluent group, as measured in this study. Caution is needed when targeting interventions to high risk groups when using single indicators. For example, the majority of births to lone mothers and to joint registrants in social classes IV and V would be missed by targeting the most deprived quintile. There is a high degree of inequality in low birth weight according to social class, area deprivation and lone mother status. When using routinely recorded birth and census data, all three factors are important to show the true extent of inequalities.