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  • Nathan Riley, MD

Obgyno Wino Podcast Episode 16 - Chronic Hypertension in Pregnancy (Part 1)

Updated: Jul 23, 2019

"The human sciences are only sciences by way of a self- flattering imposture. They run into an insurmountable limit, because the realties they aspire to understand are of the same order of complexity as the intellectual means they deploy. Therefore they are incapable of mastering their object, and always will be.” - Claude Lévi- Strauss

2016 Old Vine Zinfandel from Four Vines Winery

PB#203 - Published Decembe r2018


Five Pearls

  1. Chronic hypertension (cHTN) in pregnancy is defined as elevated BPs ≥140/90mmHg on two occasions measured at least 4 hours apart before 20 weeks gestational age (wga)

  2. There is solid evidence for starting baby aspirin (81mg) daily between 12 and 18 wga to prevent superimposed preeclampsia. It should be continued until delivery

  3. cHTN carries an increased risk for superimposed preeclampsia, renal disease, pulmonary edema, fetal growth restriction, preterm delivery, stillbirth, placental abruption, and many more bad things

  4. If you see acute, severe, persistent BP elevations, this should prompt a full work-up for superimposed preeclampsia

  5. 3rd trimester growth ultrasound are recommended as well as fetal non-stress testing, though the exact timing, frequency, and intervals between serial evaluations is not agreed upon


cHTN: defined and distinguished

- traditional definition: two elevated BPs ≥140/90mmHg measured at least 4 hours apart before 20 weeks gestational age (wga) using a properly-fitted BP cuff

-OR-

- hypertensive disease first diagnosed in pregnancy that does not resolve postpartum w/in 12 wks (data for this time interval is limited)

- 85% is "essential"; 10-15% is secondary to underlying renal, endocrine, or vascular conditions

- American College of Cardiology (ACC) and American Heart Association (AHA) have four categories of HTN:


- the recommendation per these governing bodies is now to treat nonpregnant adults with stage 1 HTN and risk factors for developing CVD in the future

- why is this important to me?! Your patients may come to you with a new pregnancy and a diagnosis of chronic ("preexisting") HTN based on these new criteria

- BUT...we are still using 140/90mmHg for newly diagnosed HTN in pregnancy (at <20 wga or later)

- ACOG recommends watching women with stage 1 HTN per the ACC/AHA guidelines more carefully in pregnancy

- stage 1 HTN carries a significantly higher risk of preeclampsia, gestational diabetes mellitus (GDM), and indicated preterm birth, and aspirin doesn't work for them (...so queue the collective shoulder shrug)

- this is an area of ongoing investigation; for now, we will continue to use these definitions:


- it's important to remember that the first and second trimesters are characterized generally by a period of vasodilation and relative hypotension (by ~10% as early as 7 wga), which may mask a HTN diagnosis in many patients

- superimposed preeclampsia diagnosis also complicated by the fact that 11% of women with cHTN have baseline proteinuria (>300 mg/day)


Your checklist at the first prenatal visit

- ideally, you should get baseline: comprehensive metabolic panel (CMP), complete blood count (CBC), liver function testing, urinalysis, spot urine protein:creatinine ratio, and EKG (if significantly abnormal, consider echocardiogram). Consider a toxicology screen, too.

- if spot urine protein:creatinine ratio is <0.15, this indicates a 24-hr urine protein collection of <300 mg (~90% sensitive); likely not necessary to get the 24-hr collection unless creatinine is abnormal

- urine creatinine may also be helpful in calculating creatinine clearance; in absence of or in mild renal impairment, creatinine clearance will increase throughout pregnancy; moderate renal impairment 50% of women will see a normal increase in creatinine clearance; in severe renal impairment, you won't see a significant increase in creatinine clearance

- HTN resistant to therapy or diagnosed at a young age should warrant investigation into secondary causes:


- if BPs in the severe range (≥160/110mmHg), initiate antihypertensive therapy (we will cover treatment regimens in Part 2)

- if they are already taking anti-hypertensive medication, discontinue ACE-I and angiotensin receptor blockers (linked to fetal growth restriction and congenital malformations such as renal dysgenesis and calvarial hypoplasia); if the patient is dependent on these specific meds, consult maternal fetal medicine (MFM)

- counseling for modifiable risk factors such as obesity, glycemic control, and smoking cessation

- make sure patient has a proper fitting cuff at home to check her BP 3-4 times daily


How does one properly check blood pressure?

- patient is rested for 10 minutes or longer

- hasn't consumed caffeine or smoked tobacco for 30 minutes or longer

- legs uncrossed

- back supported

- arm at level of heart

- cuff length is 1.5x the upper arm circumference


Risks to mom

- 5-6x increased risk of cerebrovascular accidents, pulmonary edema, or renal failure compared to normotensive pregnant women

- absolute risk of mortality and major maternal morbidity remains low

- the bad stuff happens when pressures persist in the severe range (we'll get there...)

- higher likelihood of developing GDM if you have cHTN (odds ratio 1.6), which is likely attributable to common risk factors like obesity and shared pathogenic context such as increased insulin resistance, chronic inflammation, and endothelial dysfunction

- also 1.8x increased risk for planned cesarean delivery before labor and 2x the risk of postpartum hemorrhage (PPH)


Risks to fetus

- higher risk of low birth weight (~2x greater risk) and preterm delivery w/ cHTN

- 2-4x higher risk of stillbirth (at earlier gestational ages), independent of other contributing factors such as superimposed preeclampsia, fetal growth restriction, or GDM

- increased risk for placental abruption

- the longer she has HTN and the higher the BPs, the worse the outcomes (meaning baseline proteinuria is already a bad sign as it indicated end organ damage); risk of fetal growth restriction increases to 25-40%, preterm delivery to 67%, placental abruption to up to 20%, and perinatal death to 10% in women with severe HTN, end-organ disease, or secondary HTN

- if mom develops superimposed preeclampsia, risk of fetal growth restriction is up to 50% (also further increased risk for preterm delivery and placental abruption); RR 3.6 of perinatal mortality compared to uncomplicated cHTN

- think of the fetus and placenta as an organ system...if other organs are damaged, it's likely that the precious cargo may also be damaged by this sick cardiovascular system

- lastly...emerging evidence that patients w/ cHTN expose fetus to higher risk of congenital anomalies (heart defects, hypospadias, esophageal atresia), particularly if untreated


Things to do throughout pregnancy...

- Start daily aspirin 81 mg between 12 and 18 wga to prevent superimposed preeclampsia; continue until delivery

- 3rd trimester growth ultrasound (starting at 28 wga, every 2 weeks util 34 wga if normal)

- Be on the lookout for superimposed preeclampsia; if no baseline proteinuria, then making this diagnosis is easy

- If patient exhibits proteinuria at baseline, it can be more challenging

- if you see acute, severe, persistent BP elevations, this should prompt a full work-up

- Note: SLE, renal disease, or hyperthyroidism may also present with acute, severe, and persistent BPs

- if you see this, best to do a full work-up in the inpatient settings, and fetal monitoring is recommended; look for elevated LFTs, hyperuricemia, thrombocytopenia, or elevated serum creatinine; check BPs every 4-8 hrs for 24-48 hrs while you are working her up

- Non-stress testing (NST) hasn't been shown ubiquitously been shown to improve outcomes; my practice is to start NST twice weekly starting at 32-34 wga (or earlier if present of co-morbidities or suspected IUGR)


In Part 2, I'll cover...

- treatment of elevated BPs prenatally and intrapartum

- timing of delivery

- intrapartum and postpartum considerations

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