OTTAWA — Women whose infants were delivered by a cesarean section had a nearly ninefold higher risk of developing a postpartum venous thromboembolism, compared with women who had a vaginal delivery, based on a review of more than 80,000 deliveries in Canada during a 6-year period.
In addition, the median time to the onset of symptoms from venous thromboembolism (VTE) was 5 days after delivery, a time when most of the women had already been discharged and were home.
“It's therefore important to educate women about the signs and symptoms of VTE so that they can get timely medical care and reduce the risk of morbidity and mortality from VTE,” Dr. Tannys Vance said at the annual clinical meeting of the Society of Obstetricians and Gynaecologists of Canada.
The study also found that the overall rate of VTE in all postpartum women was 0.05%, similar to the rate in previously reported studies from other populations.
But before now there were few data on the incidence in women after cesarean sections, compared with those who had vaginal deliveries, said Dr. Vance, an ob.gyn. at the University of Alberta, Edmonton.
The study reviewed records for 80,365 women who gave birth at any of five hospitals in the Edmonton region during January 1999-June 2005.
Dr. Vance and her associates identified 39 confirmed episodes of VTE that occurred within 3 months of delivery. The most common presentations were deep vein thrombosis (13 cases), pulmonary embolism (12 cases), and pelvic vein thrombosis (12 cases).
The average age of these women was 29 years. The median time of diagnosis was 9 days after delivery, a median of 4 days after symptoms first appeared.
The incidence of VTE following a cesarean section was 0.14%, compared with a 0.026% rate following vaginal delivery. Translated into an odds ratio, VTE after surgical delivery was 8.9 times more likely than after vaginal delivery, she said.
Other factors that significantly boosted the risk of VTE included hospitalization before delivery, bed rest before delivery, a history of peripartum blood transfusions, a history of thrombophilia, proteinuria occurring after 20 weeks' gestation, and multiple gestations.