The association between low-dose combined oral contraceptives (COCs) and anticoagulation factors in Japanese women has been rarely studied. A total of 394 Japanese women with a new beginning cycle of COC use were enrolled, of whom 335 women visited the clinic within 4 weeks after starting the first cycle of COC. Visits occurred in the active phase (272 women) and the placebo phase (63 women). Free protein S (PS) antigen and activity levels and antithrombin activity levels decreased significantly in both the active and placebo phase groups. Protein C (PC) activity levels increased significantly in both groups. Larger reductions in free PS antigen and activity levels occurred with COC comprising either 30 µg ethinylestradiol/desogestrel or 20 µg ethinylestradiol/drospirenone than that comprising 35 µg ethinylestradiol/norethisterone. In four women with the Japanese-specific PS K196E mutation, mean PS activity was 65% before COC use and 57% during COC use, indicating further decrease with COC use. In conclusion, decreased antigen and activity levels of PS and antithrombin and increased activity levels of PC were observed even during the first cycle of low-dose COC use. The effects on PS and PC activities were also observed in the hormone-free interval.

中文翻译：

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低剂量联合口服避孕药和S K196E蛋白突变对抗凝因子的影响：一项前瞻性观察研究。

很少研究低剂量联合口服避孕药（COC）与抗凝因子之间的关联。共有394名日本妇女进入了新的开始使用COC的周期，其中335名妇女在开始第一个COC周期后的4周内就诊了。在活跃阶段（272名妇女）和安慰剂阶段（63名妇女）进行了随访。在活动期和安慰剂期组中，游离蛋白S（PS）抗原和活性水平以及抗凝血酶活性水平均显着降低。两组中的蛋白C（PC）活性水平均显着增加。含有30 µg乙炔雌二醇/去氧孕烯或20 µg乙炔雌二醇/屈螺烯酮的COC所产生的游离PS抗原和活性水平的降低幅度要大于含35μg乙炔雌二醇/去甲甾酮的COC降低。在有日本特有PS K196E突变的四名女性中，平均CO活性在使用COC之前为65％，在使用COC期间为57％，表明随COC使用而进一步降低。总之，即使在低剂量COC使用的第一个周期中，也观察到PS和抗凝血酶的抗原和活性水平降低，PC活性水平升高。在无激素间隔内也观察到对PS和PC活性的影响。