Oral contraceptives and venous thrombosis: end of the debate?

Benefits and risks of oral contraceptives

The major benefits of modern low-dose oral contraceptives include relative safety and a high degree of efficacy, decreasing the need for abortion or surgical sterilization; reduced risks of bacterial (but not viral) pelvic inflammatory disease and of endometrial and ovarian cancer; improved menstrual regularity, with less dysmenorrhea and blood flow; and, when low-dose combination (not progestogen-only) oral contraceptives are used, reduced acne and hirsutism. Major risks are cardiovascular. Preliminary data from nonrandomized studies suggest that oral contraceptives containing third-generation progestogens are associated with increased risk of venous thromboembolism, particularly in carriers of the coagulation factor V Leiden mutation. The risk of arterial thrombosis, such as myocardial infarction or stroke, may be directly related to estrogen dose, particularly in women who have hypertension, smoke, or are >35 years old. Considering that only users aged >/=30 years who smoke >/=25 cigarettes/d have a higher estimated mortality rate than that of pregnant women, the benefits of oral contraceptives appear to outweigh their risks.

Oral contraceptives and vascular reactivity of great vessels in women

Blood pressure and great vessel vascular reactivity, evaluated by color Doppler ultrasound, were investigated in users of third-generation oral contraceptives (n = 18) compared to non-users, who were studied either in the follicular (n = 8) or in the luteal (n = 10) phase of the menstrual cycle. Blood pressure measured at rest in the supine position, evaluated both in the follicular phase and in the luteal phase, was similar between oral contraceptive users and non-users. The pulsatility index (an indirect index of resistance to blood flow) of both the internal carotid artery and the axillary artery was similar in control women studied in the follicular phase and in the luteal phase. By contrast, in users of oral contraceptives, pulsatility index values of the internal carotid artery tended to be higher, whilst those of the axillary artery were significantly higher, than those of women in either the follicular phase (p < 0.01) or the luteal phase (p < 0.025). In conclusion, new third-generation oral contraceptives do not have a significant impact on blood pressure control, but still tend to increase vascular resistance to blood flow, particularly in areas more involved in the regulation of blood pressure, for example the axillary artery.