Variation in severe maternal morbidity according to socioeconomic position: a UK national case-control study

Objectives: This study aimed to explore the independent association between socioeconomic position, defined by occupation, and severe maternal morbidity among women in the UK. Design: Case-control study. Setting: The analysis was conducted as a case-control analysis, using data from a series of studies of direct causes of severe maternal morbidity undertaken through the UK Obstetric Surveillance System (UKOSS), with data collected throughout all consultant-let obstetric units in the UK. Participants: The analysis included 1144 cases and 2256 comparison women (controls). UKOSS studies from which data on case women were obtained included amniotic fluid embolism, acute fatty liver of pregnancy, eclampsia, peripartum hysterectomy, therapies for peripartum haemorrhage and uterine rupture. Primary outcome measure: Odds of severe maternal morbidity by socioeconomic group, independent of ethnicity, maternal age, smoking, pre-existing medical condition, body mass index (BMI), multiple pregnancy and past pregnancy complications. Occupation was used to classify different socioeconomic groups. Secondary outcome measure: Odds of morbidity related to ethnic group, maternal age, smoking, pre-existing medical condition, BMI, multiple pregnancy and past pregnancy complications. Results: Across the socioeconomic groups, compared with the 'managerial/professional' group, adjusted ORs were 1.17 (95% CI 0.94 to 1.45) for the 'intermediate group', 1.16 (95% CI 0.93 to 1.45) for 'routine/manual', 1.22 (95% CI 0.92 to 1.61) for 'unemployed' women and 1.51 (95% CI 1.18 to 1.94) for women with missing socioeconomic information. Women of non-white ethnicity, older maternal age (>= 35 years), BMI >= 25 kg/m(2) and those with pre-existing medical condition/s, multiple pregnancy or past pregnancy complications were shown to have a significantly increased odds of severe maternal morbidity. Conclusions: This study suggests that socioeconomic position may be independently associated with an increased risk of severe maternal morbidity, although the observed association was not statistically significant. Further research is warranted to confirm this and investigate why this association might exist in a country where healthcare is universal and free at the point of access.