Social class inequalities in perinatal outcomes: Scotland 1980-2000

OBJECTIVE: To examine social class inequalities in adverse perinatal events in Scotland between 1980 and 2000 and how these were influenced by other maternal risk factors. DESIGN: Population based study using routine maternity discharge data. SETTING: Scotland. PARTICIPANTS: All women who gave birth to a live singleton baby in Scottish hospitals between 1980 and 2000 (n=1,282,172). MAIN OUTCOME MEASURES: Low birth weight (LBW), preterm birth, and small for gestational age (SGA). RESULTS: The distribution of social class changed over time, with the proportion of mothers with undetermined social class increasing from 3.9% in 1980-84 to 14.8% in 1995-2000. The relative index of inequality (RII) decreased during the 1980s for all outcomes. The RII then increased between the early and late 1990s (LBW from 2.09 (95%CI 1.97, 2.22) to 2.43 (2.29, 2.58), preterm from 1.52 (1.44, 1.61) to 1.75 (1.65, 1.86), and SGA from 2.28 (2.14, 2.42) to 2.49 (2.34, 2.66) respectively). Inequalities were greatest in married mothers, mothers aged over 35, mothers taller than 164 cm, and mothers with a parity of one or more. Inequalities were also greater by the end of the 1990s than at the start of the 1980s for women of parity one or more and for mothers who were not married. CONCLUSION: Despite decreasing during the 1980s, inequalities in adverse perinatal outcomes increased during the 1990s in all strata defined by maternal characteristics.