Decreasing incidence of placental abruption in Finland during 1980-2005.

OBJECTIVE: To study the incidence trends of placental abruption. DESIGN: Register-based retrospective study. SETTING: The Finnish Medical Birth Register and Hospital Discharge Register. POPULATION: A total of 6231 placental abruption cases among 1 576 051 deliveries. METHODS: Data on demographic and pregnancy and delivery associated outcomes were collected. Data on overall incidence and maternal age were available 1980-2005. Data on other variables were available 1987-2005. MAIN OUTCOME MEASURE: Placental abruption RESULTS: The overall incidence of placental abruption was 395/100 000 (0.4%). The incidence decreased 31%, from 487/100 000 in 1980 to 337/100 000 in 2005 (p < 0.001). The incidence was lowest among women aged 20-24 years (305/100 000) and highest among women aged ≥45 years (1309/100 000). During 1987-2005 the incidence was lowest among women with one or two deliveries (353/100 000) and highest in nulliparous women (382/100 000) and in women with three or more deliveries (595/100 000). The incidence was nearly double (577/100 000) among smoking compared with non-smoking women (341/100 000). The incidence was highest between gestational weeks 26 and 29. Among newborns weighing <1500 g the incidence was higher (5734/100 000) than among those weighing ≥2500 g (251/100 000). The incidence was higher in multiple (903/100 000) than in singleton pregnancies (374/100 000). CONCLUSION: The incidence of placental abruption decreased during 1980-2005. The incidence was highest among women aged 45 years or more, multiparous and smoking women, in multiple pregnancies and in women with low birthweight newborns.