Obstetrics in Family Medicine: A Practical Guide (Current Clinical Practice) 2nd ed.

14. Hypertension in Pregnancy

Paul Lyons¹

(1)

Department of Family Medicine, University of California, Riverside, Riverside, CA, USA

Key Points

1.

2.

3.

4.

Background

Pregnancy may be complicated by hypertension either as a pre-existing condition or as a newly diagnosed condition during pregnancy. Each condition carries with it significant risks and important management considerations that may impact the well-being of both the mother and fetus. Pre-eclampsia, a multisystem disorder that is marked by pregnancy-induced hypertension and proteinuria, is a significant obstetrical risk that affects approximately 5 % of pregnancies.

The exact cause of pre-eclampsia is unknown, but its multisystem complications are well described. Physiologically, pre-eclampsia is marked by increased vascular resistance, platelet aggregation, and endothelial dysfunction. Clinically, pre-eclampsia may be identified with hypertension (occurring after 20 weeks’ gestation), proteinuria, HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets), and seizures (eclampsia).

Chronic hypertension is defined as hypertension (repeated BP readings of systolic ≥140 or diastolic ≥90 mmHg) existing prior to pregnancy or first diagnosed prior to 20 weeks’ gestation. Obstetrical complications associated with chronic hypertension include increased risk for pre-eclampsia (discussed later), abruptio placentae, premature delivery, IUGR, fetal demise, and fetal stress. Pregnancy itself may worsen hypertensive renal disease. The majority of such complications occur in women with diastolic BPs higher than 110 mmHg although such complications may occur in women with lower BP.

Pre-eclampsia occurs in approximately 5 % of all pregnancies and may be associated with many of the same obstetrical risks as chronic hypertension (Table 14.1): HELLP syndrome (10–20 %), abruptio placentae (1–4 %), and eclampsia (<1 %). Rarely, it may also be associated with maternal stroke or death. Complications for the neonate include IUGR (10–25 %), preterm delivery (15–67 %), and perinatal death (1–2 %). For both the mother and infant, the presence of pre-eclampsia may be associated with long-term cardiovascular morbidity.

Table 14.1

Risk factors for pre-eclampsia

Diagnosis

Diagnostic Criteria

The diagnostic criteria for hypertension in pregnant patients are similar to those for nonpregnant patients. Hypertension may be diagnosed in patients with at least two BP readings of more than 140 mmHg systolic or more than 90 mmHg diastolic separated by at least 6 h but not more than 7 days.

Pre-eclampsia is diagnosed by a combination of hypertension first diagnosed after 20 weeks’ gestation and proteinuria (≥ 300 mg per 24 h or 1+ dipstick protein in two random urine samples separated by at least 4 h). In addition, hypertension associated with neurological (headache, visual changes, altered mental status), gastrointestinal (right upper quadrant pain, nausea, vomiting, elevated liver enzymes), or hematological (decreased platelet count) findings should also suggest pre-eclampsia. Ten percent of patients who develop HELLP syndrome and up to 33 % of patients who develop eclampsia will not demonstrate the traditional findings of both hypertension and proteinuria.

Severe pre-eclampsia is diagnosed if any one of the three criteria (hypertension, proteinuria, multiorgan involvement) is severe. The criterion for severe hypertension in pregnancy is a systolic BP >160 mmHg and/or diastolic BP >110 mmHg. Proteinuria is considered severe at levels 5 g or more per day. Multiorgan involvement may be demonstrated by pulmonary edema, seizures, altered mental status, headaches, visual disturbance, persistent right upper quadrant pain with elevated liver enzymes, oliguria (<500 cc/day), or thrombocytopenia (<100,000).

History

Although the diagnosis of pre-eclampsia is generally made on the basis of BP readings and proteinuria, a number of risk factors have been identified and should be reviewed in the history. These risk factors are shown in Table 14.2and include family history of pre-eclampsia, past history of pre-eclampsia, nulliparity, primipaternity, age over 40, assisted fertility, multiple gestation, chronic hypertension, diabetes mellitus, renal disease, thrombophilia obesity, maternal infection, and smoking.

Table 14.2

Complications of pre-eclampsia

In addition, all patients should be screened at each visit for symptoms suggestive of possible pre-eclampsia including headache, visual changes, altered mental status, abdominal pain, nausea, or vomiting.

Physical Examination

Each prenatal visit should include documentation of the patient’s BP. For patients who demonstrate elevated BP, a return visit should be scheduled within 1 week for a recheck of BP.

For patients with elevated BP, the physical examination should also include ophthalmological, neurological, and abdominal examinations as well as notation of peripheral edema (feet, hands, and face).

Laboratory Studies

The most accurate test for proteinuria is a 24-h urine collection with measurement of protein excretion. In settings where such collections are not practical, two separate dipstick urinalysis tests demonstrating at least 1+ protein may substitute. Additional labs for patients with suspected pre-eclampsia should include complete blood count with platelets, liver enzymes, and a coagulation panel.

Management

Chronic Hypertension

Patients with a pre-existing diagnosis of hypertension should continue to receive treatment during the course of pregnancy. Providers should review the safety of their existing antihypertensive regimen and make adjustments as necessary. Antihypertensive medications are reviewed in Chap. 4. Antihypertensive medications commonly used during pregnancy include methyldopa, hydralazine, and β-blockers. For patients diagnosed with hypertension after conception but prior to 20 weeks’ gestation, the role of antihypertensives is less clear. Patients with severe hypertension (diastolic over 110 mmHg) should probably receive pharmacological treatment but treatment of women with mild essential hypertension in pregnancy has not been shown to improve outcomes. Patients with chronic hypertension should be carefully followed for signs or symptoms of pre-eclampsia as 15–25 % will develop superimposed pre-eclampsia.

Pre-Eclampsia

Prevention

As the risk factors associated with increased risk for pre-eclampsia have become increasingly well defined, interest has been focused on prevention of pre-eclampsia in patients at high risk. Proposed interventions have included dietary supplements, aspirin, and antihypertensive medications. Although the results have been mixed, there is little evidence to support the preventive benefits of diet and exercise, protein or salt restriction, magnesium, fish oil or antioxidant supplementation, heparin, or antihypertensive medications. Although some studies have shown potential benefit with the use of low-dose aspirin or calcium supplementation, insufficient evidence exists to make general recommendations concerning their use in the prevention of pre-eclampsia.

Management

The management of pre-eclampsia involves balancing the maternal risks of prolonged pregnancy against the neonatal risks of premature delivery. The potential risks and benefits for each patient must be considered individually. Although no universally acceptable management protocol can be recommended, a general approach to the management of pre-eclampsia is outlined in Fig. 14.1.

Fig. 14.1

Management of pre-eclampsia

Delivery is the definitive maternal management plan. For this reason, delivery should occur as soon as it can reasonably be achieved. For patients at term with mild disease, induction of labor is indicated. For patients with severe pre-eclampsia at or beyond 34 weeks, delivery is indicated with appropriate neonatal support. If the maternal condition appears stable but there is evidence of fetal compromise, management should follow a protocol similar to that of IUGR (see Chap. 6).

For patients with mild disease, no evidence of fetal compromise, and a gestational age of less than 34 weeks, ideal management is not well established. Under these circumstances, careful monitoring of maternal condition should be combined with close evaluation of fetal well-being. If both maternal and fetal conditions remain stable, delivery can occur at 38 weeks. If either maternal or fetal condition worsens, delivery should occur as soon as possible.

As noted for chronic hypertension, the use of antihypertensives has shown mixed results. For patients with severe hypertension, the use of antihypertensive medications has been shown to reduce maternal cerebrovascular complications. However, such treatment has not been shown to reduce neonatal complications and does not alter the maternal course of disease in relation to multiorgan complications. The use of antihypertensives has not been shown to improve maternal or neonatal outcomes in patients with mild disease. There is little evidence to support the use of any specific class of antihypertensive medications in the treatment of pre-eclampsia.

The use of corticosteroids has not been shown to improve maternal outcomes, although their use has been shown to improve neonatal outcomes for infants born prior to 34 weeks’ gestation.

Seizure Prevention

Seizure (eclampsia) is one of the most significant complications of pre-eclampsia and may occur without preceding warning signs. For this reason, seizure prophylaxis with magnesium sulfate is indicated for patients with pre-eclampsia in the intrapartum period. Specific regimens for the use of magnesium may vary between institutions and the specific protocol should be reviewed by each provider. One possible protocol is as follows: loading dose of 6 g of intravenous magnesium sulfate followed by 2 g per hour of continuous intravenous infusion. Magnesium may be toxic in high doses and patients should be monitored closely while undergoing magnesium therapy. Maternal BP, deep tendon reflexes, mental status, and urinary output should be monitored. Serum magnesium levels should be measured. Magnesium levels above 7 mEq/L are associated with diminished deep tendon reflexes. Magnesium levels above 10 mEq/L are associated with respiratory depression. Magnesium levels above 12 mEq/L are associated with cardiac depression and arrest. Magnesium elevation is reversible with 10 % calcium gluconate 10 mL intravenous given over 10–15 min.