hypertension%20in%20pregnancy
HYPERTENSION IN PREGNANCY
Hypertension in pregnancy is defined as an average diastolic blood pressure of ≥90 mmHg, based on at least 2 measurements, ≥4 hr apart or systolic blood pressure of ≥140 mmHg taken at least 6 hr apart.
Diagnosis of severe hypertension is made when blood pressure is ≥160/110 mmHg.
Measurement should be repeated after 15 min for confirmation.

Delivery

Delivery
  • Close maternal and fetal surveillance is required as prompt delivery is indicated by worsening maternal condition, lab tests showing end-organ dysfunction or fetal distress
    • The decision to deliver in women with preeclampsia should not depend on the degree of proteinuria or change in the amount of proteinuria
    • In any type of hypertensive disease in pregnancy, vaginal delivery should be considered unless cesarean delivery is required for the usual obstetric indications
    • Severe hypertension is not, in itself, an indication for cesarean delivery
    • For patients with hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome, cesarean delivery may increase the risk of bleeding due to thrombocytopenia and difficulty in blood pressure (BP) control due to diminished intravascular volume
  • Delivery within 24 hours is indicated in patients with uncontrolled severe hypertension showing signs of maternal and fetal deterioration, regardless of gestational age or fetal lung maturity
  • For women with preeclampsia before 34 weeks age of gestation (AOG), corticosteroids should be administered to accelerate fetal lung maturity
Indications for Delivery
  • Maternal
    • AOG ≥37 weeks
    • Platelet <100,000 cells/mm3 or disseminated intravascular coagulation
    • Uncontrolled hypertension
    • Eclampsia
    • Pulmonary edema
    • Progressive deterioration of liver or renal function
    • Suspected abruptio placentae
    • Persistent severe headache or other cerebral or visual disturbances
    • Persistent epigastric pain, nausea and vomiting
  • Fetal
    • Severe growth restriction
    • Non-reassuring fetal testing results
    • Oligohydramnios

Pharmacotherapy

Centrally-Acting Agents
  • Act centrally to reduce sympathetic tone causing a decrease in blood pressure (BP)
  • Lower BP effectively
Methyldopa
  • Considered 1st-line agent for hypertension in pregnancy
  • Safe to use in pregnancy, without reports of maternal or fetal adverse effects
    • Long-term pediatric follow-up has confirmed safety record
  • Reports show that Methyldopa continues stable uteroplacental blood flow and hemodynamics
Beta-Blockers
  • May be used as initial therapy for hypertension in pregnancy as they are nonteratogenic
  • Comparative trials of beta-blockers and methyldopa have shown that beta-blockers may be more effective in BP reduction than methyldopa, but no significant difference in maternal or perinatal outcomes have been demonstrated

Labetalol

  • Oral Labetalol is the preferred beta-blocking agent
    • Agent of choice if Methyldopa is not tolerated
  • Intravenous (IV) Labetalol is considered the 2nd-line agent in treatment of acute hypertension in preeclampsia, rapidly controls severe resistant hypertension
  • Noncardioselective beta-blocker with selective alpha1 blocking properties that decreases peripheral vascular resistance causing vasodilatation and decreases BP more rapidly than other beta-blockers
Acebutolol, Metoprolol, Pindolol and Propranolol
  • These agents have not been associated with any adverse effects when administered in late pregnancy
  • Competitive antagonists of the effects of catecholamines at beta-adrenergic receptor sites
    • Beta1 receptors are found mainly in the heart while beta2 receptors are usually found in non-cardiac tissues including bronchial, peripheral blood vessels, uterus and pancreas
    • Blockade of beta1 receptors reduces heart rate (HR), myocardial contractility and the rate of conduction of impulses through the conducting system along with adrenergic-induced renin release and lipolysis
    • Beta2 blockade can increase bronchial resistance and inhibition of catecholamine-induced glucose metabolism
  • Lower BP effectively
    • Beta blockers have different affinities for beta1 or beta2 blockade but as doses are increased, activity of beta2 receptors can become apparent in beta1 selective inhibitors
  • Atenolol, when given in pregnancy, has been linked to low weight for gestational age
Calcium Antagonists
  • Experience with oral calcium (Ca) antagonists in pregnancy is limited with most uses reported in late pregnancy
  • No increase in major teratogenicity with exposure to Ca antagonists has been shown
  • Inhibit the cellular influx of Ca which is responsible for maintenance of the plateau phase of the action potential
    • The cells they affect are typically the vascular smooth muscle, myocardial cells and cells within the sinoatrial (SA) and atrioventricular (AV) nodes
    • They dilate coronary and peripheral arteries with little or no effect on venous tone, have a negative inotropic action, reduce HR and slow AV conduction
  • Lower BP effectively
  • May cause myocardial depression when combined with magnesium (Mg)
Nifedipine
  • Used as 2nd-line antihypertensive in pregnancy
  • The preparations of Nifedipine appropriate for use in pregnancy are capsule and prolonged action tablet
    • A study has shown safety and efficacy of long-acting Nifedipine taken orally in pregnant women with severe hypertension in pregnancy
    • A distinction should be made between short-acting Nifedipine for treatment of severe hypertension and both intermediate-acting prolonged action and slow-release Nifedipine for non-severe hypertension
  • Stat dose of oral Nifedipine 10 mg may be used for rapid BP control in acute hypertensive crisis
Nicardipine
  • Considered as a second-line alternative when IV bolus Labetalol, Hydralazine or oral Nifedipine did not relieve acute severe hypertension in pregnant women
Diuretics
  • Use of diuretics in pregnancy is controversial due to theoretical risk of decreasing plasma volume, causing or exacerbating preeclampsia
    • However, they appear to be safe and efficacious in practice and may be administered if required
  • Some authorities recommend the use of diuretics only in combination with other agents especially when vasodilators exacerbate fluid retention
  • Lower BP effectively and potentiate the response to other antihypertensive agents
  • Please refer to Hypertension Disease Management Chart for dosage guidelines of diuretics
Angiotensin Converting Enzyme (ACE) Inhibitors/Angiotensin II Antagonists
Contraindicated in pregnancy
  • May cause fetal growth restriction, oligohydramnios, neonatal renal failure and neonatal death
  • Stop ACE inhibitors or angiotensin II antagonists prior to attempts at conception or when pregnancy is confirmed
    • Replace with Methyldopa or beta-blockers that are considered safe during pregnancy
Direct Vasodilators
Hydralazine
  • Hydralazine IV has been used widely to control severe preeclampsia
  • Acts directly on the arterioles causing vasodilatation, causing a decrease in peripheral resistance and BP
  • Oral hydralazine when used for chronic hypertension has been found to be inferior to other agents
    • IV Hydralazine is effective in treatment of high BP associated with preeclampsia; however, it has been associated with more perinatal side effects such as maternal hypotension, placental abruption, oliguria, neonatal thrombocytopenia and lower APGAR score
Sodium (Na) Nitroprusside
  • Last-line agent for acute hypertension in preeclampsia, should only be used when other agents fail to reduce BP
  • Acts directly on arterioles and veins causing peripheral vasodilatation that results in a decrease in peripheral resistance and BP
  • Short-acting hypotensive, lowers BP effectively for 1-10 minutes
    • Reduces BP rapidly causing excessive hypotension
  • Converts rapidly into cyanide and thiocyanate causing cyanide accumulation and thiocyanate toxicity, thereby, increasing the risk of fetal cyanide poisoning
Anticonvulsant
Magnesium (Mg) sulfate (Parenteral)
  • Used to prevent recurrent convulsions in eclampsia or convulsions in preeclampsia
  • Reduces frequency of eclampsia in pregnancy-induced hypertension or severe preeclampsia and decreases the incidence of placental abruption
  • Decreases acetylcholine in motor nerves and acts on myocardium by slowing rate of SA node impulse formation and prolonging conduction time
Aspirin
  • Meta-analyses showed Aspirin may reduce preeclampsia and adverse perinatal outcomes
  • May be given at a low dose at the start of the late 1st trimester in women with a history of preeclampsia and preterm delivery at <34 weeks of gestation or has had preeclampsia in >1 pregnancy
    • Low-dose Aspirin may also be offered to women with chronic hypertension from 12 weeks of gestation

Non-Pharmacological Therapy

Women with Low-Risk Hypertension
  • Consider non-drug therapy
  • May taper and stop any existing antihypertensive therapy
  • Prior to conception, stop angiotensin converting enzyme (ACE) inhibitors or angiotensin II antagonists

Postpartum Hypertension

Potential Complications
  • Women with hypertension that persists postpartum may develop complications eg encephalopathy, heart failure, pulmonary edema and renal failure postpartum
Considerations
  • Resolution of high blood pressure (BP) is usually more rapid in patients with gestational hypertension
  • Delayed resolution may occur in patients who suffered preeclampsia and especially in those who had longer duration of preeclampsia and greater renal impairment
    • Greatest risk of occurrence of postpartum eclampsia is within the first 48 hours
Treatment
  • Magnesium sulfate may be continued 12-24 hours after delivery or longer to prevent postpartum eclampsia
  • Continue oral antihypertensive treatment in severe postpartum hypertension to keep BP below 160/110 mmHg
  • Continue oral antihypertensive treatment in non-severe postpartum hypertension, if with comorbidities
Treatment of Hypertension During Lactation
  • Breastfeeding is encouraged
Mild Hypertension
  • For mothers who want to breastfeed for a few months
    • May withhold medications with close monitoring of BP and reinstate treatment after discontinuation of lactation
Severe Hypertension (treated with single antihypertensive)
  • May consider reducing dose of antihypertensive with close observance of mother and infant
  • Recommendations:
    • If a beta-blocker is indicated, Propranolol and Labetalol are preferred
    • No short-term adverse effects have been reported with Methyldopa or Hydralazine
  • Agents to avoid:
    • Atenolol, Metoprolol and Nadolol concentrate in breast milk
    • Diuretics decrease milk volume and suppress lactation
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