[Association between low-dose oral contraceptive use and stroke in Chinese women]

To investigate the association between low-dose combined oral contraceptive (COC) widely distributed in China and the risk of hemorrhagic stroke so as to decrease the adverse reaction of COC.

A prospective cohort study was made among 44 408 women who took hormonal contraceptives (HCs) and 75 230 women who used in trauterine device (IUD) in 25 townships and toens in Rudong County and Taicang City, Jiangsu Province, to compare the incidence of stroke among them from 1 July 1997 to 30 June 2000.

(1) The incidence of hemorrhagic stroke (age-and-county standardized rates) was 34.74 per 100 000 py in the HC cohort, 2.72 times higher than that in the IUD cohort (P < 0.01). The incidence of hemorrhagic stroke among women less than 45 years of age was remarkably higher in HC cohort than in the IUD cohort. The relative risk of incidence of hemorrhagic stroke was 2.17 (1.16, 4.06) among the HC users who had stopped HC use for more than 10 years, still significantly higher than among the IUD users. (2) The relative risk of incidence of hemorrhagic stroke among the women who used low-dose COCs during the survey was 3.60 (1.73, 7.53) times higher than that among the IUD users. The relative risk of incidence of hemorrhagic stroke was 3.09 (1.26, 7.57) among the women who had stopped low-dose COC use for less than five years, however, the risk of hemorrhagic stroke remarkably decreased after they stopped taking COC for more than 5 years. (3) No obvious increase in incidence of infarctional stroke was found among the women who took low-dose COC during the survey. (4) Hypertension might be the most important risk factor of hemorrhagic stroke among the low-dose COC users.

There is an obvious increase in risk of hemorrhagic stroke among the Chines women who take low-dose of China-made COCs for a long time. The efffect of China-made COCs on pathogenesis of hemorrhagic stroke lasts sometime after the discontinuation of COC use.