Objective To characterise changing risk factors of preterm birth in Western Australia between 1984 and 2006.Design Population-based study.Setting Western Australia.Population All non-Aboriginal women giving birth to live singleton infants between 1984 and 2006.Methods Multinomial, multivariable regression models were used to assess antecedent profiles by preterm status and labour onset types (spontaneous, medically indicated, prelabour rupture of membranes [PROM]). Population attributable fraction (PAF) estimates characterized the contribution of individual antecedents as well as the overall contribution of two antecedent groups: pre-existing medical conditions (including previous obstetric history) and pregnancy complications.Main outcome measure Antecedent relationships with preterm birth, stratified by labour onset type.Results Marked increases in maternal age and primiparous births were observed. A four-fold increase in the rates of pre-existing medical complications over time was observed. Rates of pregnancy complications remained stable. Multinomial regression showed differences in antecedent profiles across labour onset types. PAF estimates indicated that 50% of medically indicated preterm deliveries could be eliminated after removing six antecedents from the population; estimates for PROM and spontaneous preterm reduction were between 10 and 20%. Variables pertaining to previous and current obstetric complications (previous preterm birth, previous caesarean section, pre-eclampsia and antepartum haemorrhage) were the most influential predictors of preterm birth and adverse labour onset (PROM and medically indicated).Conclusions Preterm antecedent profiles have changed markedly over the 23years studied. Some changes may be attributable to true change, others to advances in surveillance and detection. Still others may signify change in clinical practice.

Aims To compare maternal and neonatal outcomes for Australian-born women with gestational diabetes mellitus with those of culturally and linguistically diverse and non-culturally and linguistically diverse foreign-born women with gestational diabetes. Methods A total of 205 616 singleton births in Western Australia between 1998 and 2006 were examined using multivariate logistic regression. Risks of ten maternal and neonatal outcomes associated with gestational diabetes were compared for pregnancies with gestational diabetes to foreign-born women from both culturally and linguistically diverse and non-culturally and linguistically diverse backgrounds vs. Australian-born women. The same outcomes were also compared for pregnancies without gestational diabetes. Results Foreign-born culturally and linguistically diverse women were more likely to undergo emergency Caesarean section, but less likely to have pre-eclampsia, an elective Caesarean section or induced labour than Australian-born women. Their infants were less likely to be large for gestational age, require resuscitation or be transferred to specialist care. These differences were also evident among pregnancies without gestational diabetes to culturally and linguistically diverse women, but did not exist between foreign-born non-culturally and linguistically diverse women and Australian-born women with gestational diabetes. Conclusions While gestational diabetes places women and infants at increased risk of adverse perinatal outcomes, these outcomes differed for foreign-born women from culturally and linguistically diverse backgrounds when compared with Australian-born women. Further investigation is required to elucidate why being foreign-born and culturally and linguistically diverse reduces the risk of several of these outcomes.