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  • Title: Haemostatic function changes in Singapore women using Norplant implants: a four year review.
    Author: Singh K, Viegas OA, Ratnam SS.
    Journal: Adv Contracept Deliv Syst; 1991; 7(2):147-56. PubMed ID: 12284217.
    Abstract:
    The effects of progestogens on hemostatic function seems to be minimal, however, in this longterm surveillance study of the effects of Norplant among 100 healthy, nonsmoking, nonalcohol drinking, and nonlactating Singaporean women indicates the possibility of an increased predisposition of thrombosis. Clinical assessment and blood sampling were taken prior to insertion and at 6, 12, 24, 36, and 48 months. Laboratory tests included prothrombin time (PT), activated partial thromboplastic time (APTT), hematocrit and platelet count as hemostatic measures. Also measured were fibrinogen, coagulation factor II, a 1-stage assay for factors V and VII, factor VII, factor X, antithrombin III, plasminogen activator activity on the fibrin plate and FDP, platelet aggregation, factor VIIIR. 20 normal controls not on any medication were used and international standards were applied in most cases. The coefficients of variation of the various tests with reference control plasma or sera are summarized. The paired t test was used to assess statistical differences. Skewed results were analyzed with the Wilcoxon signed rank test. % changes between pre- and postinsertion levels were also utilized. The results were that the hemoglobin concentration increased from 12.1 gm/dl to 13.4 gm/dl in the 1st year, and then decreased to preinsertion levels within 3 years, and increased to 13.3 gm/dl in the 4th year. The 4th year also reflected no menstrual disorder. PT and APTT appeared significantly shortened in year 1. PT continued to shorten in 3 more years, while APTT increased to the preinsertion mean. Vitamin K dependent factors II and VII decreased significantly in year 1, while factors V and X increased significantly. Factor II increased minimally within 2 more years, but decreased again in year 4. Factor VII continued to decrease over the 4 years. The concentration of factors II and VII were significantly lower after 4 years. Factor V increased 14.4% in year 1, but decreased below preinsertion levels in the next 3 years, and then decreased to preinsertion levels in year 4. No significant changes in fibrinolytic activity occurred in 4 years. Major changes occurred in mean platelet count, which rose significantly in year 1 and increased concentration in year 4. In 4 years, platelet aggregation using ADP or equine collagen rose significantly. Serious thought must be given to the risk of thrombosis and potential for hypercoagulation.
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