Are sociodemographic factors predictive of preterm birth? A reappraisal of the 1958 British Perinatal Mortality Survey

Objective Reassessment of the predictive value of sociodemographic factors on preterm birth. Design Population-based case-control study. Setting England, Wales and Scotland. Sample The study sample consisted of 5630 primiparous and 9538 multiparous women who were delivered during the first week of March 1958 in Britain. Multiple births were excluded. Method Factors potentially predictive of preterm birth were assessed for primiparous and multiparous women separately, using the split-sample cross-validation technique. Main outcome measure Preterm birth, defined as birth occurring before 259 days of gestation. Results Preterm birth rates for primiparous and multiparous women were 54 and 53 per 1000 births, respectively. In primiparous women low maternal age (under 20 years) was the only sociodemographic variable that was predictive of preterm birth (P = 0.01). However, only 10.7% of preterm birth among primiparous women was associated with low maternal age. In multiparous women, using univariable analysis, employment status was statistically significantly associated with preterm birth. This association disappeared when employment status was adjusted for by other variables in the model. Social class was not predictive of preterm birth in either primiparous or multiparous women. Conclusion From the results of this study it is concluded that sociodemographic factors do not have a substantial impact on the risk of preterm birth. It seems unlikely that preventative measures aimed at social-demographic adversity will reduce preterm birth rates.