Hemostasis profile in women taking low-dose oral contraceptives

Article Abstract:

The risk of blood clot formation (thrombosis) is reduced in women taking low-dose oral contraceptive formulas over those taking earlier compounds. It is thought that the hormones contained in the formulas cause changes in the blood clotting mechanisms that promote the formation of clots, which can block blood vessels in the heart, lungs, brain and legs. The effect of oral contraceptives on the blood clotting mechanism is reported among 36 nonsmoking women. Women were given either of two widely used low-dose oral contraceptive formulas, Marvelon, a pill containing 30 micrograms of ethinyl estradiol and 150 milligrams of desogestrel, or Trigynon, in a pill sequence that delivers over a three-week period different doses of ethinyl estradiol and levenorgesterol. After six months of therapy, there were no differences in blood clotting variables in the two pill formula groups, so the results were combined for the two groups. There was no change in the number of platelets (cells that clump during clotting), the platelet aggregating ratio (circulating clumps), or levels of thromboglobulin (released from platelets). There was an increase in the von Willebrand factor, a substance released from platelets and the cells lining blood vessels (endothelial cells) which helps platelets to adhere. Factor VIII:C, factor VII:C and fibrinogen (the substance that is converted to fibrin, the protein basis of clots) were also elevated. The plasminogen concentration and activity were increased, a fact that may be related to the effect of estrogen on the production of required proteins in liver cells. Antithrombin III activity, an inhibitor of blood clotting, was not reduced, despite a reduction in its concentration. There was a shortening of euglobulin lysis time (the time required for breakdown of clots) and partial thromboplastin time, a test of coagulation. It is thought that in some women, there is a defect in the protective plasminogen activator/inhibitor system predisposing them to thrombotic events. (Consumer Summary produced by Reliance Medical Information, Inc.)

Oral contraceptives

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Changes in hemostasis activity during delivery and the immediate postpartum period

Article Abstract:

Activation of the blood coagulation system is thought to occur at the time of delivery. This is evidenced by the development of deep vein thrombosis, the formation of a blood clot in the deep veins of the legs, in the postpartum period. Coagulation occurs through the interaction of a number of factors, namely platelets, fibrinogen, factor VIII and plasminogen. It is not clear whether the balance of the clotting system is altered through a change in the production or the consumption of coagulation factors. New advances in blood analysis permit the measurement of markers in the blood that indicate clotting activity. The blood markers reveal the degree of fibrinolysis (mechanism of clot dissolving) and activation of platelets (cells that aggregate during clotting). These markers were used to study the changes in hemostatic activity experienced during delivery and immediately afterwards. Tests to measure 11 blood clotting functions were performed on 70 healthy pregnant women. There was an increase in activation of platelets and formation of fibrin, a stringy protein found in clots, at the time of delivery. The clotting system is activated immediately after the delivery of the placenta and this activation continues for the first three postpartum hours. Fibrinolysis is increased in the first three hours postpartum, followed by gradual decrease in activity during the next 48 hours. Women who do not experience a dramatic increase in fibrinolytic activity during the postpartum period may be at risk for deep vein thrombosis. (Consumer Summary produced by Reliance Medical Information, Inc.)

Risk factors, Thrombophlebitis, Blood clotting, Blood coagulation

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Changes in 24-hour heart rate variability during normal pregnancy

Article Abstract:

Heart rate fluctuations occur less often than usual during pregnancy. This was the conclusion of researchers who measured heart rate variability using Holter monitors on eight healthy pregnant women early in their pregnancy, at 10, 18 and 34 weeks of pregnancy, and again when they were not pregnant. Heart rate variability decreased during pregnancy, especially during the first six weeks after conception, and the respiration rate increased.

Heart beat, Heart rate

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