Nephrology Hypertension

Hypertension in Pregnancy

Does this pregnant patient have hypertension?

How do you diagnose and treat hypertension in a pregnant patient?

Hypertension accompanies pregnancy in 5-10% of women, depending on the population. The main categories of hypertension in pregnancy include:

  • Preexisting hypertension: This is defined as systolic pressure >= 140 mmHg and / or diastolic pressure >= 90 prior to pregnancy, present before the 20th week of pregnancy, or present more than 12 weeks post-partum. This complicates approximately 3% of pregnancies.

  • Gestational hypertension: This is defined as systolic pressure >= 140 mmHg and / or diastolic pressure >= 90 , NO proteinuria, AFTER the 20th week of gestation in women previously normotensive. Blood pressure should be elevated on at least two occasions at least 6 hours apart. Present in 6% of pregnancies. This diagnosis is changed to pre-eclampsia if proteinuria develops or chronic hypertension if it persists past 12 weeks postpartum. Recurrence is relatively high at 20-47%.

  • Pre-eclampsia: This is defined as systolic pressure >= 140 mmHg and / or diastolic pressure >= 90 and proteinuria of 0.3 grams or more in a 24-hour urine specimen. Blood pressures should be documented on at least 2 occasions, no less than 6 hours, but no more than 7 days apart. Recurrence risk is about 5%t at term. Pre-eclampsia occurs in 5-8% of pregnancies in the United States, classified as severe in 25% of cases. About 25% of patients initially diagnosed with gestational hypertension progress to pre-eclampsia. Risk factors for its development include prior pre-eclampsia, first pregnancy, family history, multiple gestations, obesity, renal disease, and advanced maternal age.

What tests to perform?

Symptoms and signs

Severity of hypertension shoud be assessed. It is considered "severe" when the systolic blood pressure is > 160 mmHg and/or diastolic blood pressure is > 110 mmHg. Patients should be monitored for symptoms of pre-eclampsia such as severe headaches, visual changes, epigastric pain, nausea, vomiting. Signs include decreased urine output.

Fetal symptoms and signs

These should be assessed with a biophysical profile or nonstress test with amniotic fluid estimation. Ultrasonographic estimation of fetal weight is appropriate.

Lab testing

Measure protein excretion to distinguish between types of hypertension. Dipstick measurement can be used as screening, but can result in false positives and negatives. In hypertensive patients, a 24-hour urine collection is the most widely accepted for measurement. A diagnosis of pre-eclapmsia is made with 0.3 grams of protein or more in the collection. A urine protein-to-creatinine ratio in a random urine sample is reasonable if a 24 hour urine cannot be collected, but is not considered the gold standard. Elevated serum creatinine concentrations, hepatic transaminases, and/or lactate dehydrogenase can be seen in pre-eclampsia.

How should pregnant patients with hypertension be managed?

There is sparse data from randomized control trials to guide therapy. Medication management with antihypertensive agents is reserved for more severe hypertension because data from randomized control trials show that medical therapy does not improve maternal or neonatal outcomes.

Bedrest appears to diminish the severity of hypertension, but not the progression rates to pre-eclampsia. This is a therapy that is quite disruptive, can result in venous thromboemoblic disease, and is probably not necessary for patients with chronic stable hypertension. Usually bedrest can be reserved for patients with pre-eclampsia and poorly controlled hypertension.

Many advise initiating antihypertensive therapy at systolic pressures of > 150-160 and diastolic pressures of > 100-110. The main indication of antihypertensive therapy is prevention of stroke. Target levels are < 160/110, at minimum, although others aim for 140-150/90-100. Lowering blood pressure more aggressively may be harmful. In patients with known end-organ damage, goals should be < 140/90.

Choice of drug in long term therapy: all antihypertensives cross the placenta. Initial therapy recommendations often include labetolol orally started at 100mg, two to three times daily, with a maximum total dose of 1200mg/day. Methyldopa has been found to be safe, but has sedative effects and is not particularly potent. Dose is 250mg twice a day to start, up to 3 gm/day. Long acting nifedipine, started at 30mg a day, titrated up to 60mg twice daily, has been used without many problems in pregnant women. Agents to be avoided include angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, and renin inhibitors due to birth defects primarily seen after the first trimester, but there are reports of defects in the first trimester as well. Patients should be taken off these agents if they are attempting to become pregnant.

Weekly office visits should be considered for patients with gestational hypertension, with delivery by 40 weeks (Grade 2C data).

Early delivery can be considered for patients with severe hypertension and/or pre-eclampsia. Prompt delivery is the therapy of choice in patients progressing to eclampsia. This would include magnesium sulfate for seizure prophylaxis. Delivery at 37 weeks gestation is suggested an a multicenter trial of over 700 patients that looked at labor induction at 37 weeks versus expectant management. There were fewer adverse maternal outcomes, a lower rate of cesarean sections, and was less costly with induction of delivery. Antenatal steroids (betamethasone) should be given to women diagnosed wtih pre-eclampsia between 24 and 34 weeks gestation.

What happens to pregnant patients with hypertension?

Most women with gestational hypertension become normotensive within the first week postpartum. By definition, all should be normotensive by week 12, otherwise they are given the diagnosis of chronic hypertension. This occurs in approximately 15% of patients with gestational hypertension.

How to utilize team care?

Patients with any form of hypertension in pregnancy should be considered for a high-risk obstetrics consultation. Therapy can also be co-managed with a hypertension specialist, such as a well-versed nephrologist.

Pharmacists can assist with ensuring drug safety in pregnant women, and can assist with possible drug interactions in pregnant patients who may be taking more than one medication.

Dietitians can assist with healthy diets with appropriate quantities of sodium for patients with hypertension.

Are there clinical practice guidelines to inform decision making?

The American College of Obstetrics (ACOG) recommends magnesium sulfate for prevention of seizures in patients with severe pre-eclampsia and the World Health Organization (WHO) recommends the same for prevention of eclampsia in women with pre-eclampsia (no distinguishing between mild and severe disease). (Grade 1A)

What is the evidence?

Abalos, E, Duley, L, Steyn, DW, Henderson-Smart, DJ. "Antihypertensive drug therapy for mild to moderate hypertension during pregnancy". Cochrane Database Syst Rev Jan. vol. 24. 2007. pp. CD002252.

Lindheimer, MD, Taler, SJ, Cunningham, FG. "Hypertension in pregnancy". J Am Soc Hypertens Mar-Apr. vol. 4. 2010. pp. 68-78.

Podymow, T, August, P. "Postpartum course of gestational hypertension and pre-eclampsia". Hypertension in Pregnancy. vol. 25. 2006. pp. 210.

Visintin, C, Mugglestone, MA, Almerie, MQ. "management of hyeprtensive disorders during pregnancy: summary of NICE guidance". BMJ. vol. 341. 2010. pp. c2007.

Tuffnell, DJ, Shennan, AH, Waugh, JJ. "The management of severe pre-eclampsia/eclampsia". Royal College of Obstetricians and Gynaecologists. 2006.

Thangaratinam, S, Coomarasamy, A, O’Mahoney, F. "Estimation of proteinuria as a predictor of complications for pre-eclampsia: a systematic review". BMC Medicine. vol. 7. 2009. pp. 1-9.

Davison, JM. "Renal disorders in pregnancy". Curr Opin Obstet Gynecol. vol. 3. 2001. pp. 109-114.

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