Low‐dose oral contraceptives and 24‐hour ambulatory blood pressure

OBJECTIVE: To evaluate in normotensive women the influence of low-dose oral contraceptives (OC, monophasic formulations containing 30 microg of estrogen) on 24-h blood pressure. METHODS: We evaluated prospectively in 15 normotensive healthy women (three smokers) the influence of OC on 24-h ambulatory blood pressure monitoring (ABPM). ABPM was performed (SpaceLabs 90207) before and after 6-9 months of use of OC. We also evaluated ABPM in eight women (two smokers) before and after 6-8 months on an intrauterine device (IUD) as contraceptive method--these were used as control subjects. RESULTS: OC produced a significant increase in 24-h ABPM values (from 120+/-3/75+/-2 to 128+/-4/81+/-2 mmHg, P < 0.04) which was particularly evident for night-time values (from 108+/-2/64+/-2 to 120+/-4/73+/-2 mmHg, P < 0.02). After OC, two normotensive women developed 'hypertensive values'. In OC users there was a slight but significant increase in body weight which did not correlate with the increase of blood pressure. In contrast, in the control group (IUD) neither ABPM values nor weight were modified by the contraceptive maneuver. CONCLUSIONS: In normotensive women, low-dose OC may increase blood pressure to an extent that, at least in some women, may affect blood pressure control towards 'hypertensive values'. This stresses the importance of monitoring blood pressure values during OC treatment.