A population-based study of venous thrombosis in pregnancy in Scotland 1980-2005

Objectives Data on time trends in the incidence of pregnancy-related venous thromboembolism (VTE) are sparse. This report charts the incidence of pregnancy-related VTE over the period 1980-2005 in Scotland, and discusses the results in relation to potential risk factors. Study design 1 475 301 maternity discharges from Scottish hospitals recorded on the Scottish Morbidity Record 2 (SMR2) were included. Incidences of pregnancy-related VTE, antenatal deep venous thromboembolism (DVT), postnatal DVT and pulmonary embolism (PTE) were derived relative to the number of deliveries, and risk factors were analysed using Poisson regression. Results Over the period, VTE incidence rose from 13.7 to 18.3 per 10 000 deliveries, antenatal DVTs from 8.8 to 12.2 per 10 000 deliveries and PTE from 1.5 to 3.0 per 10 000 deliveries. Postnatal DVTs, on the other hand, declined from 4.2 to 2.7 per 10 000 deliveries. Risk factors were: age over 35 years; three or more previous pregnancies; previous VTE; obstetric haemorrhage; and preeclampsia. Antenatal DVT risk was highest in the most deprived areas, where events started increasing before those in less deprived areas. Postnatal DVT risk was increased following caesarean delivery, especially when unplanned, although after 1996, events following emergency caesarean decreased. Conclusion During the 26-year period, pregnancy-related VTEs increased, with the greatest rise for antenatal DVTs. Postnatal DVTs, on the other hand, declined over the period, particularly following emergency section. Thromboprophylaxis use following emergency delivery may have led to the postpartum reduction. To continue to prevent events, risk assessment and intervention are required, particularly antenatally.