Clinical Review

Controlling chronic hypertension in pregnancy

OBG Manag. 2006 February;18(2):56-55

References

1. Ferrer RL, Sibai BM, Murlow CD, Chiquette E, Stevens KR, Cornell J. Management of mild chronic hypertension during pregnancy:a review. Obstet Gynecol. 2000;96:849-860.

2. Sibai BM, Abdella TN, Anderson GD. Pregnancy outcome in 211 patients with mild chronic hypertension. Obstet Gynecol. 1983;61:571-576.

3. Chobanian AB, Bakris GL, Black HR, et al. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 Report. JAMA. 2003;289:2560-2572.

4. Sibai BM, Lindheimer M, Hauth J, et al. Risk factors for preeclampsia, abruptio placentae, and adverse neonatal outcomes among women with chronic hypertension. N Engl J Med. 1998;339:667-671.

5. Sibai BM. Chronic hypertension in pregnancy. Obstet Gynecol. 2002;100:369-377.

6. Umans JG, Lindheimer MD. Antihypertensive treatment. In:Lindheimer MD, Roberts JM, Cunningham FG, eds. Chesley’s Hypertensive Disorders in Pregnancy. 2nd ed. Norwalk, Conn:Appleton and Lange; 1998:581-604.

7. Abalos E, Duley L, Steyn DW, Henderson-Smart DJ. Antihypertensive drug therapy for mild to moderate hypertension during pregnancy. In: The Cochrane Library, Issue 12, 2003. Oxford:Update Software.

8. How HY, Sibai BM. Use of angiotensin-converting enzyme inhibitors in patients with diabetic nephropathy. J Matern Fetal Neonatal Med. 2002;12:402-407.

9. Sibai BM, Mabie WC, Shamsa F, Villar MA, Anderson GD. A comparison of no medication versus methyldopa or labetalol in chronic hypertension during pregnancy. Am J Obstet Gynecol. 1990;162:960-966.

10. Sibai BM, Villar MA, Mabie BC. Acute renal failure in hypertensive disorders of pregnancy:pregnancy outcome and remote prognosis in thirty-one consecutive cases. Am J Obstet Gynecol. 1990;62:777.-

11. Mabie WC, Ratts TE, Ramanathan KB, Sibai BM. Circulatory congestion in obese hypertensive women:a subset of pulmonary edema in pregnancy. Obstet Gynecol. 1988;72:553-558.

12. Lie RT, Rasmussen S, Brunborg H, et al. Fetal and maternal contributions to risk of pre-eclampsia:a population based study. Br Med J. 1998;316:1343-1347.

13. Briggs GG, Freeman RK, Yaffee SJ. Drugs in Pregnancy and Lactation:A Reference Guide to Fetal and Neonatal Risk. 5th ed. Baltimore:Williams & Wilkins;1998.

14. White WB. Management of hypertension during lactation. Hypertension. 1984;6:297-300.

15. Zhang J, Meikle S, Trumble A. Severe maternal morbidity associated with hypertensive disorders in pregnancy in the United States. Hypertens Pregnancy. 2003;22:203-212.

16. Rey E, Couturier A. The prognosis of pregnancy in women with chronic hypertension. Am J Obstet Gynecol. 1994;171:410-416.

17. McCowan LM, Buist RG, North RA, Gamble G. Perinatal morbidity in chronic hypertension. Br J Obstet Gynaecol. 1996;103:123-129.

18. August P, Helseth G, Cook EF, Silson C. A prediction model for superimposed preeclampsia in women with chronic hypertension during pregnancy. Am J Obstet Gynecol. 2004;191:1666-1672.

CHARACTERISTIC	PREECLAMPSIA (%)
Age (yr)
≤35	26
>35	25
Previous preeclampsia
Yes	32
No	23
Duration of hypertension
<4 years	23
≥4 years	32
Diastolic blood pressure (mm Hg)
<100	24
100-109	25
≥110	40-50
Thrombophilia	40-50
Diabetes mellitus	30-40
Proteinuria
No	25
Yes	27
Note: Risk is also increased in women with multifetal gestation and in those who have conceived using assisted reproductive technology.
Source: Sibai BM, et al⁴

Low-risk hypertension

Stop drugs at first visit

Women with low-risk chronic hypertension without superimposed preeclampsia usually have pregnancy outcomes similar to those in the general obstetric population.^2,5,9

Discontinuation of antihypertensive therapy early in pregnancy does not increase the rates of preeclampsia, abruptio placentae, and preterm delivery in these women.^2,9

Our policy is to discontinue antihypertensive treatment in low-risk women at the first prenatal visit, because most of these women have good outcomes without such therapy.

Follow-up strategy

During subsequent visits, we educate the patient about nutritional requirements, weight gain, and sodium intake (maximum of 2.4 g sodium per day). We also remind them that alcohol use and smoking during pregnancy can aggravate maternal hypertension and cause adverse effects in the fetus such as fetal growth restriction and abruptio placentae.

During the remainder of the pregnancy, we observe the gravida very closely for appropriate fetal growth and early signs of preeclampsia.

Fetal evaluation should include an ultrasound examination at 16 to 20 weeks’ gestation, to be repeated at 32 to 34 weeks and monthly thereafter until term. In addition, all women with low-risk hypertension should undergo growth scans starting at 32 to 34 weeks, especially obese women in whom fundal height measurements are unreliable, because of the increased risk of intrauterine growth restriction.

If severe hypertension develops before term, start either nifedipine or labetalol (TABLE 6).

Immediate fetal testing with the nonstress test or biophysical profile is necessary if severe hypertension, preeclampsia, abnormal fetal growth, or evidence of oligohydramnios develops.

Hospitalization and delivery are necessary if severe hypertension, fetal growth restriction documented by ultrasound, or superimposed preeclampsia develops at or beyond 37 weeks.

If none of these complications is present, pregnancy can continue until 40 weeks’ gestation.⁵

TABLE 3

Diagnosis of preeclampsia in women with preexisting conditions

PREEXISTING CONDITION	PREECLAMPSIA IS PRESENT IF SHE HAS…
Hypertension	Proteinuria ≥500 mg/24 hours or thrombocytopenia or abnormal liver enzymes
Proteinuria	New onset hypertension plus symptoms and/or thrombocytopenia or elevated liver enzymes
Hypertension plus proteinuria (renal disease or class F diabetes)	New onset of persistent symptoms (severe headache, visual changes) or thrombocytopenia or elevated liver enzymes

TABLE 4

Complication rates in women with superimposed preeclampsia vs women without hypertension*

COMPLICATION	WITHOUT HYPERTENSION (PER 1,000 CASES)	PREECLAMPSIA SUPERIMPOSED ON CHRONIC HYPERTENSION (PER 1,000 CASES)
Abruptio placentae	9.6	30.6
Thrombocytopenia	1.6	11.5
Disseminated intravascular coagulation	2.9	17.4
Pulmonary edema	0.2	6.4
Blood transfusion	1.5	16.3
Mechanical ventilation	0.2	17.0
*US women, 1988–1997
Source: Zhang J, et al¹⁵

High-risk hypertension

The frequency and nature of maternalfetal adverse effects depends on the cause of the hypertension and the extent of target organ damage.

Realistic preconception counseling

Women with substantial renal insufficiency (ie, serum creatinine >1.4 mg/dL), diabetes with vascular involvement (class R/F), severe collagen vascular disease, cardiomyopathy, or coarctation of the aorta should be advised that the pregnancy might exacerbate their condition. These patients should be made aware of the potential for congestive heart failure, acute renal failure requiring dialysis, and even death. In addition, perinatal loss and neonatal complications are markedly increased in these women.

Refer or consult a specialist

All women with severe hypertension should be managed in consultation with a subspecialist in maternal-fetal medicine, as well as any other specialists who may be indicated.

They also should be observed and delivered at a tertiary care center with adequate maternal-neonatal care facilities.⁵

TABLE 5

Adverse pregnancy outcomes in women with mild chronic hypertension

OBSERVATIONAL STUDY	PREECLAMPSIA (%)	ABRUPTIO PLACENTAE (%)	DELIVERY AT <37 WEEKS (%)	SMALL FOR GESTATIONAL AGE (%)
Sibai et al² (n=211)	10.0	1.4	12.0	8.0
Rey and Couturier¹⁶ (n=337)	21.0	0.7	34.4	15.5
McCowan et al¹⁷ (n=142)	14.0	Not reported	16.0	11.0
Sibai et al⁴ (n=763)	25.0	1.5	33.3	11.1
August et al¹⁸ (n=110)	34.0	Not reported	Not reported	8.0

Management strategy

Our policy is to hospitalize women with high-risk hypertension at the time of the first prenatal visit to evaluate their cardiovascular and renal status and regulate antihypertensive medications, as well as other prescribed drugs (eg, insulin, cardiac drugs, thyroid drugs). Women receiving atenolol, ACE inhibitors, or angiotensin II receptor antagonists should have these medications discontinued under close observation.

In women without target organ damage, the aim of antihypertensive therapy is to keep systolic pressure between 140 and 150 mm Hg and diastolic pressure between 90 and 100 mm Hg.

In women with target organ damage and mild hypertension, antihypertensive therapy is also indicated, because there are short-term maternal benefits to lowering blood pressure. We recommend keeping systolic pressure below 140 mm Hg and diastolic pressure below 90 mm Hg.

Early, frequent visits.Women with high-risk chronic hypertension need close observation throughout pregnancy and may require serial evaluation of 24-hour urine protein excretion and a complete blood count with a metabolic profile at least once every trimester. Further laboratory testing depends on the clinical progress of the pregnancy. At each visit, remind the woman about the adverse effects of smoking and alcohol use, and counsel her about the importance of diet and minimal salt intake.⁵