Contributor: MFM Division
Last Update: 5/1/2010
Depending on the population studies and the criteria used, the incidence of chronic hypertension in pregnancy is 0.5% to 3 %. The etiology of chronic hypertension can be divided into primary (essential or idiopathic) and secondary. About 10% of chronic hypertension (cHTN) in pregnancy is secondary representing a myriad of causes.
- Renal disease- glomerulonephritis, interstitial nephritis, nephropathy, polycystic kidneys, renal transplant
- Collagen vascular disease- lupus erythematosus, periarteritis nodosum, scleroderma
- Endocrine disease- diabetes, hyperaldosteronism, pheochromocytoma, hyperthyroidism
- Vascular disease- coarctation of the aorta, renal artery stenosis
The diagnosis of cHTN is based on the presence of a systolic BP of > 140 mm Hg or a diastolic BP of >90 mm Hg on at least two occasions 4-6 hours apart before 20 weeks. Women who meet this criteria and have no history of HTN, who are < 30 yo with severe HTN (BP > 160/110) should be evaluated for secondary hypertension as outlined at the end of this guideline.
The maternal risks of cHTN include preeclampsia and placental abruption. The rate of superimposed preeclampsia is 5-25% and the rate of placental abruption ranges from 1-10% depending on the severity of the HTN or superimposed preeclampsia.
The perinatal risks are related to maternal complications and severity of HTN. The rate of perinatal mortality amoung 298 women with cHTN was 45/1000 compared with a rate of 12/1000 in the general population. High rates of preterm delivery (20-60%) and SGA infants (11-30%) are seen in clinically hypertensive gravidas.
At time of diagnosis review history for cardiac or renal disease, diabetes, thyroid dysfunction and the outcome of prior pregnancies.
- Baseline laboratory studies should include urinalysis, BMP, CBC, and 24 hour urine collection to measure creatinine clearance and protein concentration. If hypertension has been present > 5 years, obtain EKG and ophthalmic examination. If new onset severe range HTN, send UDS to evaluate for cocaine.
- In general, patients will be continued on the antihypertensive medications they currently are on. Avoid ACE inhibitors and ACE receptor inhibitors in women of child bearing age or stop them preconceptionally. Patients with concurrent diabetes should have medications adjusted to keep BPs < 140/90.
- Obtain early obstetric ultrasound combined with first trimester screening (if desired) to firmly establish dates.
- Encourage multiple marker screening testing (MMST) at 15-21 weeks.
- Obtain fetal anatomy scan at 18-22 weeks.
- Obtain serial growth scans beginning around 26 weeks if on medication (IV).
- Institute antihypertensive if BP > 160/105 on two occasions 6 hours apart and no signs or symptoms of superimposed preeclampsia. The goal of therapy is BPs < 160/105 (except in patients with pregestational diabetes where the goal is <140/90).
- Labetalol 100 mg po q 8 hrs up to maximum of 2400 mg/day
- Nifedipine 10 mg po q 6 hrs OR 30 gm XL po qd up to maximum of 120 mg/day
- Alpha-methydopa 250 mg po bid up to maximum of 2 grams/day
- Patients are at risk for superimposed preeclampsia and IUGR. Begin antenatal fetal testing if IUGR or superimposed preeclampsia develops at > 26 weeks.
- Patients with a history of hypertension on no medication do not require antenatal testing.
- If no earlier indication arises, patients with cHTN on medication should begin testing at > 34 weeks. In the Ob Center this will most frequently be twice weekly NSTs and once weekly AFI measurements. The exception is the hypertensive patient with “good control” on medication without IUGR or other comorbidities who may be monitored once weekly with an AFI and NST.
- Nonreassuring fetal status should lead to further testing or delivery.
- If cervix is favorable and dating is reasonable, patients should be induced during the 39th week of gestation. Consideration for earlier delivery may be made if other risk factors exist.
- Use antihypertensives in labor to keep BPs <160/110 (Ia).
- Postpartum continue patients on current medications and refer for appropriate medical follow up. During antenatal care at the Ob Center, referral should be made to New Horizons for a one time visit to establish ongoing follow up unless the patient has a primary care physician.
The secondary causes of hypertension are the identifiable causes of hypertension. Based on the etiology of the hypertension appropriate medical referral can be made.
Renal causes consist of anything that results in acute or chronic renal failure. An abnormal BUN, creatinine and urinalysis suggest renal failure. Further evaluation begins with a renal ultrasound and a referral to Nephrology.
Adrenal causes consist of Cushing’s syndrome, primary aldosteronism and pheochromocytoma. Cushingoid features suggest Cushing’s syndrome of any cause including iatrogenic. Screening is done with a 24 hour urinary free cortisol level. Spontaneous and marked hypokalemia suggests primary aldosteronism. Screening is done with a 24 hour urinary aldosterone level. Symptoms or signs of sympathetic nervous system overload suggest pheochromocytoma. Screening is done with 24 hour urinary levels of catecholamines, VMA and metanephrines.
Vascular causes consist of coarctation of the aorta and renal artery stenosis. A heart murmur with symptoms of poor perfusion of the lower extremities suggests coarctation. An EKG may reveal LVH. Screening is performed with Echocardiography. Abdominal or flank bruits with lab studies that suggest renal disease suggest renal artery stenosis. BPs in the upper extremities may differ suggesting this diagnosis. Screening during pregnancy is best accomplished with duplex ultrasonography of the renal arteries.
Collagen vascular disease will be suggested by patient history and physical exam. Endocrine causes are also suspected based on history. If symptoms of diabetes exist, assess a FBS or 1 hour glucola. If symptoms of hyperthyroidism are present, a TSH and free T4 can be evaluated.
- Sibai BM. Chronic hypertension in pregnancy. Obstet Gynecol 2002;100:369-77.
- 2007 Compendium, Vol II. Chronic hypertension in pregnancy;609-15.
- Sibai BM. Hypertensive disorders in women. WB Saunders Co: 2001; 125-38.
- Huls CK, Shah DM. Chronic hypertension. In Queenan JT, Spong CY, Lockwood CJ, (eds). Management of High-Risk Pregnancy. Malden, MA: Blackwell Publishing Ltd, 2007:210-13.
- Abalos E, Duley L, Steyn DW et al: Antihypertensive drug therapy for mild to moderate hypertension during pregnancy (Cochrane Review). In Cochrane Library, Issue 2. Oxford, Update Software, 2001.