Maternal risk factors associated with preterm birth <32 weeks' in non-tertiary hospitals

Background: Over the past decade, the proportion of preterm births <32 weeks' gestation in non-tertiary hospitals in Victoria has increased. Reducing rates of preterm birth in non-tertiary hospitals is contingent on early recognition and prompt in-utero transfer of high-risk women to a tertiary perinatal centre. The aim of this study was to investigate maternal risk factors associated with preterm birth <32 weeks' gestation in non-tertiary hospitals.Method: Data were analysed for a population-based cohort of all livebirths, 22 to 31 weeks' gestation born in Victoria, Australia between 1990 and 2009. Maternal data for non-tertiary (“outborn”) compared with tertiary (“inborn”) births were analysed as covariates in a logistic regression model, with “outborn” as the dependent variable.Results: 13,760 livebirths were recorded. 1,985 (14%) were outborn and 11,775 were inborn. Compared with mothers of inborn livebirths, a significantly higher (p < 0.001) proportion of the mothers of outborn livebirths were multigravidas (OR 1.37; 95% CI 1.24, 1.51) and were teenagers (OR 2.02; 95% CI 1.67, 2.45). They had a higher rate of spontaneous preterm labour (OR 4.42, 95% CI 3.86, 5.07) and were more likely to deliver vaginally (OR 3.21; 95% CI 2.89, 3.56). A higher proportion of outborn births were associated with an antepartum haemorrhage. Women with hypertensive disorders, pre-labour rupture of membranes and multiples were more likely to give birth in a tertiary centre.Conclusions: This study has identified obstetric risk factors associated with preterm birth in non-tertiary hospitals. Further strategies to facilitate timely in-utero transfer of high-risk women are required.