Chronic hypertension in pregnancy: Clinical sciences

Chronic hypertension in pregnancy is defined as an elevated blood pressure that’s present prior to conception or first identified before 20 weeks of gestation. This condition requires increased surveillance because of the significant risks to the patient, including stroke, renal insufficiency, superimposed preeclampsia with or without severe features, placental abruption, and postpartum hemorrhage; as well as the risks to a fetus like congenital anomalies, growth restriction, and preterm birth.

Your first step is to perform a CABCDE assessment and conduct a primary obstetric survey.

If the patient is unstable, first check for uncontrolled bleeding and control any hemorrhage, as severely elevated blood pressures may cause a placental abruption.

Next, stabilize their airway, breathing, and circulation, and consider intubation when appropriate. Obtain IV access and continuously monitor maternal vital signs, especially blood pressure.

Perform your primary obstetric survey, which includes monitoring the fetal heart rate as well as possibly testing for rupture of amniotic membranes and checking cervical dilation.

Alright, let’s talk about stable patients. Start by obtaining a focused history and physical exam, and measure their blood pressure. History might reveal pre-existing hypertension, and your patient may already be taking antihypertensive medications. As for their blood pressure, measure it on two separate occasions at least 4 hours apart. If both measurements show a systolic blood pressure of 140 mmHg or more, a diastolic blood pressure of 90 mmHg or more, or both, that’s hypertension.

So, if your patient has pre-existing hypertension, or develops newly elevated blood pressures before 20 weeks of gestation, you can diagnose chronic hypertension in pregnancy.

Here’s a clinical pearl! The normal physiologic changes of pregnancy generally cause a patient's blood pressure to decrease in the first half of pregnancy and then rise to preconception levels by about 36 weeks of gestation. As such, some patients who initially meet criteria for chronic hypertension may not have another elevated blood pressure until later in their pregnancy; however it’s important to continue to treat them for chronic hypertension due to the high risk of adverse pregnancy outcomes.

The treatment varies depending on the phase of obstetric care; let’s start with antepartum patients.

First, assess estimated gestational age, or EGA for short. If your patient is at less than 20 weeks of gestation, obtain baseline labs, including a CBC to assess for anemia and thrombocytopenia; a CMP to evaluate renal and liver function; a urine protein-to-creatinine ratio to assess for proteinuria; and possibly a 24-hour urine collection to assess total urine protein.

Here’s a clinical pearl! The kidneys are usually the first organ to be affected by chronic hypertension. So, if either the creatinine or the protein-to-creatinine ratio is abnormal, order a 24-hour urine collection to further assess for baseline proteinuria. This is helpful to either follow a known elevated urine protein throughout pregnancy or to help distinguish new onset proteinuria later on.

Additionally, obtain an early pregnancy ultrasound to establish an accurate due date, and plan on obtaining a fetal anatomic survey at 20 weeks of gestation to assess for structural anomalies. Lastly, get an electrocardiogram. If it’s abnormal or your patient has additional risk factors for cardiomyopathy, such as obesity or a long-standing history of hypertension, consider an echocardiogram as well.

Next, start your patient on daily low-dose aspirin, optimally between 12 to 16 weeks, though it could be beneficial up to 28 weeks, and continue it until delivery to help prevent progression to superimposed preeclampsia. Additionally, consider starting an antihypertensive medication if your patient has persistently elevated blood pressures of greater than or equal to 140 systolic, 90 diastolic, or both. Preferred antihypertensives are labetalol or nifedipine; while hydrochlorothiazide is considered a second-line agent.

Here’s a high-yield fact! Make sure your pregnant patient is not taking an ACE inhibitor, an angiotensin 2 receptor blocker, a renin inhibitor, or a mineralocorticoid receptor blocker, as these could result in fetal malformations.

Okay, let’s go back to assessing EGA and talk about patients who are at least 20 weeks of gestation.

In this case, your first step is to assess the need for antihypertensive medications. As long as blood pressures are consistently less than 140 systolic and less than 90 diastolic, antihypertensives are not needed. Remember, these patient’s have already been diagnosed with chronic hypertension but at this time have either normotensive or mildly elevated pressures not requiring medication. For these patients, obtain routine prenatal labs, and a fetal ultrasound in the third trimester, to ensure there are no complications like fetal growth restriction or oligohydramnios. Delivery is indicated between 38 to 39 weeks and 6 days of gestation.

Alright, let’s talk about patients with EGA of at least 20 weeks who have persistently elevated blood pressures of at least 140 systolic, 90 diastolic, or both. These patients require assessment for superimposed preeclampsia by checking labs, such as a CBC, CMP, urine protein-to-creatinine ratio, and possibly a 24-hour urine protein to check for proteinuria, which is defined as a urine protein-to-creatinine ratio greater than or equal to 0.3, or a 24-hour urine collection with at least 300 mg of protein.