Use of antihypertensive therapy

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In women who have an elevated blood pressure but do not have true pre-eclampsia and do not require admission to hospital, antihypertensive therapy can be introduced. In the United Kingdom during the past 20 years, the use of antihypertensive drugs has increased (Walker, 2000). This has been associated with a reduction in the incidence of cerebral vascular accident as a cause of maternal mortality, although other factors may be involved.

If blood pressure is above 160/100 mmHg, treatment is started in an effort to reduce the risk of hypertensive crisis, the need for further antihyper-tensive therapy and the need for a hospital admission. Methyldopa and labetalol are the most common antihypertensive therapies used in pregnancy (Magee et al., 1999). Methyldopa has proven safety in terms of long-term follow up of delivered babies (Ounsted et al., 1980). Labetalol would appear to be at least equally safe (Magee and Duley, 2000) but atenalol is associated with an increase in fetal growth restriction. Because of fears concerning fetal affects, angiotensin-converting enzyme (ACE) inhibitors are contraindicated beyond the first trimester (Magee, 2001) although there are case reports of successful outcome where there is no alternative (Muller and James, 2002; Tomlinson et al., 2000).

Although some have suggested starting treatment at lower levels, delaying the treatment of hypertension in pregnancy until DBP is 100 mmHg is not associated with additional maternal or fetal risk and reduces the number requiring treatment by 50% (Walker, 1991).

Since methyldopa has significant maternal side effects, it has been the authors' practice to use labetalol starting at 200mgbd increasing in increments to a maximum of 1200 mg a day (Walker, 1991). In a prospective double-blind randomized placebo-controlled study of 144 women who developed mild pre-eclampsia after 20 weeks gestation, labetalol significantly lowered blood pressure and reduced the incidence of progression to pre-eclampsia. However, there did not appear to be a benefit in late-onset disease, and therefore the appropriateness of pharmacologic therapy for late onset mild pre-eclampsia may be questioned (Pickles et al., 1992). Labetalol does appear to be well-tolerated with no significant maternal toxicity (Cruickshank et al., 1992). Various studies have demonstrated that in labetalol-treated patients there is less progression to severe disease and a reduction in hospital inpatient antenatal stay without any detrimental effect on fetal outcome. There is a trend toward prolongation of pregnancy, reduction in emergency Cesarean sections and an increase in vaginal deliveries.

Therefore, as long as there is no immediate reason to admit to hospital, antihypertensive therapy can be started safely as an outpatient in the ADU where continued monitoring of the mother and baby can be made on a weekly basis. This appears to be associated with a reduction in hospital admission, prolongation of pregnancy and a reduction of progression to more severe disease (Magee etal., 1999).

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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