The risk of preterm delivery in women from different ethnic groups

Abstract

Objective To examine whether routinely measured variables explained the increased risk of preterm delivery in some UK ethnic groups. Design Cross sectional study of deliveries recorded in the Child Health Record System. Setting North Birmingham, UK. Population All North Birmingham women delivering singletons, 1994–1997 inclusive. Method Logistic regression. Main outcome measures Odds ratio (OR) and 95% confidence interval (CI) for preterm delivery, defined as less than 37 weeks, less than 34 weeks and less than 28 weeks, unadjusted and adjusted for maternal age, an area-based socio-economic status measure, and marital status, year of birth, fetal sex and past obstetric history. Results For Afro-Caribbean women, the ORs (95% CIs) were: for delivery less than 37 weeks, 1.44 (1.26–1.64) unadjusted and 1.22 (1.07–1.41) adjusted; for delivery less than 34 weeks, 1.55 (1.25–1.92) unadjusted and 1.29 (1.02–1.61) adjusted; for delivery less than 28 weeks, 1.66 (1.08–2.55) unadjusted and 1.32 (0.84–2.06) adjusted. For African women, the risk of delivery less than 37 weeks was not significantly raised; for delivery less than 34 weeks, the OR (95% CI) was 1.88 (0.99–3.58) unadjusted and 1.78 (0.93–3.40) adjusted; for delivery less than 28 weeks, the OR (95% CI) was 4.02 (1.60–10.12) unadjusted and 4.10 (1.66–10.16) adjusted. In Afro-Caribbeans, deprivation and marital status explained the differences between the unadjusted and adjusted ORs. There was a linear relation between deprivation and preterm delivery for all ethnic groups, except for Asians. Conclusions Factors associated with deprivation and marital status explain about half of the excess of preterm births in Afro-Caribbeans, but not Africans. The risk of preterm delivery might not be related to deprivation in Asians.