Management of hypertension before, during, and after pregnancy

Abstract

ypertension is the most common medical problem encountered in pregnancy and remains an important cause of maternal, and fetal, morbidity and mortality.It complicates up to 15% of pregnancies and accounts for approximately a quarter of all antenatal admissions.The hypertensive disorders of pregnancy cover a spectrum of conditions, of which pre-eclampsia poses the greatest potential risk and remains one of the most common causes of maternal death in the UK. NORMAL PHYSIOLOGICAL CHANGE IN BLOOD PRESSURE DURING PREGNANCY cEarly in the first trimester there is a fall in blood pressure caused by active vasodilatation, achieved through the action of local mediators such as prostacyclin and nitric oxide.This reduction in blood pressure primarily affects the diastolic pressure and a drop of 10 mm Hg is usual by 13-20 weeks gestation. 1Blood pressure continues to fall until 22-24 weeks when a nadir is reached.After this, there is a gradual increase in blood pressure until term when pre-pregnancy levels are attained.Immediately after delivery blood pressure usually falls, then increases over the first five postnatal days.w1 Even women whose blood pressure was normal throughout pregnancy may experience transient hypertension in the early post partum period, perhaps reflecting a degree of vasomotor instability. DEFINITION OF HYPERTENSION IN PREGNANCY AND BLOOD PRESSURE MEASUREMENTHypertension in pregnancy is diagnosed either from an absolute rise in blood pressure or from a relative rise above measurements obtained at booking.The convention for the absolute value is a systolic .140 mm Hg or a diastolic .90 mm Hg.However, it should be recognised that blood pressure is gestation related.A diastolic blood pressure of 90 mm Hg is 3 standard deviations (SD) above the mean for mid pregnancy, 2 SD at 34 weeks, and 1.5 SD at term.w2 The definition for a relative rise in blood pressure incorporates either a rise in systolic pressure of .30 mm Hg or rise in diastolic pressure of .15 mm Hg above blood pressure at booking.Blood pressure must be elevated on at least two occasions and measurements should be made with the woman seated and using the appropriate cuff size.Late in the second trimester and in the third trimester, venous return may be obstructed by the gravid uterus and, if supine, blood pressure should be taken with the woman lying on her side.Korotkoff phase I and V (disappearance) should be used, rather than phase IV (muffling), since it is more reproducible 2 and shows better correlation with true diastolic blood pressure in pregnancy. 3 If phase V is not present, phase IV should be recorded.Automated systems for blood pressure measurement have been shown to be unreliable in severe pre-eclampsia w3-4 and tend to under record the true value. CLASSIFICATION OF HYPERTENSIVE DISORDERS OF PREGNANCYThere are three types of hypertensive disorders: c chronic hypertension c gestational hypertension c pre-eclampsia Chronic hypertensionChronic hypertension complicates 3-5% of pregnancies 4 although this figure may rise, with the trend for women to postpone childbirth into their 30s and 40s.The diagnosis of chronic hypertension is based on a known history of hypertension pre-pregnancy or an elevated blood pressure > 140/90 mm Hg before 20 weeks gestation. 5However, there are several caveats to this diagnosis.Undiagnosed hypertensive women may appear normotensive in early pregnancy because of the normal fall in blood pressure, commencing in the first trimester.This may mask the pre-existing hypertension w5 w6 and when hypertension is recorded later in the pregnancy it 1499 www.heartjnl.