Effect of low-dose aspirin on vascular refractoriness in angiotensin-sensitive primigravid women

Article Abstract:

Pregnancy is associated with changes in the reactions of blood vessels, specifically, during pregnancy there is an increased likelihood of blood vessel dilation (relaxation) and a diminished response to angiotensin II, a substance that causes blood vessel constriction. (This diminished response to angiotensin II during pregnancy is referred to as a refractory response.) Blood vessel changes in pregnancy may result from altered production of eicosanoids, such as prostaglandins and thromboxanes. Studies suggest that prostacyclin, which causes blood vessel dilation and prevents the aggregation of platelets (cells involved in blood clotting), has a greater influence during pregnancy than thromboxane A2, which causes blood vessel constriction and platelet aggregation (clumping). However, primigravid women (in their first pregnancy) may have insufficient prostacyclin production, such that the effects of thromboxane A2 dominate. The subsequent vasoconstriction and enhanced platelet aggregation may lead to the development of hypertension, or abnormally high blood pressure. Primigravid women also have increased sensitivity to angiotensin II, which may contribute to the development of pregnancy-related hypertension. A daily dose of 60 milligrams of aspirin prevents the development of pre-eclampsia, a pregnancy-related hypertensive condition. Aspirin prevents thromboxane A2 production and corrects the imbalance between thromboxane A2 and prostacyclin. Low-dose aspirin may also restore the normal response to angiotensin II. The effect of a low dose of aspirin, taken daily from the 28th to the 34th week of pregnancy, on the blood vessel response to angiotensin II was assessed. The study involved 36 primigravid women with normal blood pressure and enhanced sensitivity to angiotensin II. Eighteen women were treated with aspirin and the remainder were given an inactive placebo. The production of thromboxane A2 was suppressed in the women who were treated with aspirin. The normal response to angiotensin II was restored in 14 of 17 aspirin-treated women and 5 of 15 women given a placebo. These findings are consistent with theories concerning the role of thromboxane A2-prostacyclin imbalance in the development of enhanced angiotensin II sensitivity in primigravid women. (Consumer Summary produced by Reliance Medical Information, Inc.)

Hypertension, Physiological aspects, Drug therapy, Pregnancy, Thromboxane synthetase

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The angiotensin sensitivity test and low-dose aspirin are ineffective methods to predict and prevent hypertensive disorders in nulliparous pregnancy

Article Abstract:

A test used to predict which pregnant women will develop high blood pressure may not be accurate, and low doses of aspirin may not prevent high blood pressure of pregnancy when it is given after 28 weeks of pregnancy. Researchers evaluated the ability of the angiotensin II sensitivity test to predict high blood pressure on 495 British women experiencing their first pregnancy. The angiotensin II test became widely used after it was found to predict high blood pressure in young black American women. Eleven percent of women who tested negative on the angiotensin II sensitivity test later developed high blood pressure, which was quite severe in some cases. Low doses of aspirin did not prevent high blood pressure in women who tested positive for angiotensin II sensitivity.

Diagnosis, Preeclampsia

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Does aspirin have a role in improving pregnancy outcome for women with the antiphospholipid syndrome? A randomized controlled trial

Article Abstract:

Low-dose aspirin does not appear to be beneficial in in preventing miscarriage in pregnant women with antiphospholipid syndrome. This syndrome is defined as recurrent miscarriage in women who have anti-phospholipid antibodies. In a study of 40 such women, the rate of live birth was 80% in those who took aspirin and those who did not.

Care and treatment, Prevention, Antiphospholipid syndrome, Miscarriage

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