The average normal incidence of thrombophlebitis in nonpregnant women of childbearing age is one case per 1,000 women per year based on data from hospital admissions, and 2.2 cases per 1,000 women per year based on data from visits to the physician. The antepartum incidence is 0.5 cases per 1,000 women per nine months. In studies with oral contraceptives, the average incidence was 0.5 cases per 1,000 women per year. Evidence does not indicate that the administration of oral contraceptives to women with a history of thrombophlebitis increases the chance of recurrence of the disease. Data in the United States do not demonstrate an increase in death rate from pulmonary embolism, and vital statistics for England do not show an increase in the ratio of women to men dying from thromboembolic diseases since the introduction of oral contraceptives.
Drill VA, Calhoun DW. Oral Contraceptives and Thromboembolic Disease. JAMA. 1968;206(1):77-84. doi:10.1001/jama.1968.03150010025004