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Hypertension in Pregnancy

Speaker:Khalid A. Yarouf

Faculty of Medicine & Health Sciences (FMHS)

Obstetrics / Gynecology Rotation 2001/02

. www.4MedStudents.com

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Outline

Physiologic adaptations in normal pregnancy.Hypertension in Pregnancy:o Definition.o Prevalence.o Classification.o Risk factors.o Pathogenesis.o Complications.o Diagnosis & Evaluation.o Management.o Self-assessment.

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Physiologic adaptations in normal pregnancy

Blood changes: o ↑ Plasma volume by ≈ 40%.o Platelets count can ↓ below 200 X 109/L due to normal

maternal blood-volume expansion.o ↑ Coagulation factors (Fibrinogen, Factor VII).

Cardiovascular changes:o Marked generalized vasodilation (↓ peripheral resistance)

a/w arterial resistance to constrictor actions of Angiotensin II.o ↑ CO & Stroke volume.o MAP ↓ by 10 mm Hg.

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Con’t

Renal changes:o Vasodilation ↑ Renal blood flow ↑ GFR (by 50%).o ↑ in Creatinine clearance with a concomitant ↓ in S-

Creatinine & urea.o ↑ Uric acid clearance & Ca+ excretion.o ↑ Glucosuria + aminoaciduria.

Respiratory changes.

Endocrine changes:o e.g. parathyroid, adrenal, weight, GI changes.

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Hypertension in Pregnancy

Definition:o = Sustained ↑ BP @ bed rest on 2 occasions at least

6 hours apart.Prevalence: 10% of all pregnancies.Classification:– Pre-eclampsia.– Chronic hypertension (HTN).– Transient HTN = Gestational HTN.

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A. Pre-eclampsia

Characteristic triad:o = Sustained HTN + Proteinuria + Edema (not

essential for Dx).o Onset > 20 weeks’ gestation.

50% of all HTN in pregnancies.Resolves after delivery.

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1. Mild pre-eclampsia

Commonest entity has NO symptoms.Characteristics:o HTN BP ≥140 / 90 mm Hg OR

↑ sBP by 30 mm Hg above non-pregnant.↑ dBP by 15 mm Hg above non-pregnant.

o Proteinuria (1-2+ dipstick OR > 300 mg / 24 hr).o Edema:

(non-dependent, hands &/ face, a/w excessive wt gain)

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2. Severe pre-eclampsia

Less common.

Can be diagnosed on basis of:– Severe HTN (BP ≥ 160 / 110 mm Hg). OR– Severe proteinuria (3-4+ dipstick OR > 5 g / 24 hr)

alone without symptoms. OR– Only mild HTN + proteinuria if signs and symptoms

are present:

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Con’t

Resp: Plum. Edema, cyanosis.Cardiac: Congestive Cardiac Failure (CCF).Renal: Proteinuria, ↑ Serum creatinine, oliguria.Hepatic: ↑ LFTs, RUQ / epigastric pain.Neurologic: visual disturbance (i.e. scotomas, loss of peripheral vision), headache, convulsions.GI: severe nausea / vomiting.Hematologic:

thrombocytopenia, microangiopathic hemolysis.

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Con’t

HELLP syndrome:o Type of severe pre-eclampsia.o Hemolysis + Elevated Liver enzymes + Low Platelets.

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3. Eclampsia

[Latin = convulsions]= Unexplained tonic-clonic seizures

+ Mild / severe pre-eclampsia.Most often occurs intra-partum (50%), but can also occur ante-partum & post-partum.

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B. Chronic HTN

Pt may have any disease causing HTN:– e.g. essential HTN, A/c & chronic GN, chronic

pyelonephritis, SLE.

1. Uncomplicated:o Definition:

= Pre-existing HTN. OR= HTN diagnosed ≤ 20 weeks. OR= HTN persisting ≥ 6 weeks post-partum.

o NOT induced by pregnancy.

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Con’t

2. Complicated by superimposed pre-eclampsia:o = Isolated HTN without proteinuria.o Characterized by: worsening of HTN ± proteinuria

+ severe PIH symptoms late in pregnancy.

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C. Transient HTN

= Late HTN = Gestational HTN.

= Non-sustained (transient) ↑ BP without proteinuria / symptoms in last half of pregnancy.Has no impact on pregnancy outcome.

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Risk Factors of Pre-eclampsia

Maternal Factors:1. Demographic criteria:

o Primagravida commonest risk factor.o Age extremes (<20 years, > 34 years).

2. Medical complications:o DM + Chronic HTN + Pre-existing renal disease + SLE.

3. Past Hx or FHx of pregnancy-induced HTN.Fetal factors:

o Hydatidiform mole, > 1 fetus, fetal hydrops, IUGR.

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Pathogenesis of Pre-eclampsia

Pre-eclampsia / eclampsia is justly called “a disease of theories”. Despite extensive research, no definite cause has been identified. As the term toxemia indicates, the search for a toxin has been long, arduous, and fruitless.Because of the prompt resolution of disease following delivery, most attention has been focused on placenta & its membranes and on fetus.Uteroplacental ischemia is postulated to be the center to the development of disease, which results in production of toxin that enters circulation and causes widespread endothelial dysfunction.

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Complications

Maternal:1. Cerebral hemorrhage (50% of deaths).2. LVF / Pulm. edema.3. Liver / renal dysfunction.4. Seizures.5. DIC.6. Abruptio placenta: ante-partum painful vaginal bleeding.

Fetal: due to placental insufficiency:1. Fetal loss.2. IUGR.3. Prematurity.

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Diagnosis & Evaluation

HTN is the most diagnostic sign. Because there’re no specific diagnostic investigations, the initial Dx of pre-eclampsia remains clinical.Hx:– Previous HTN or proteinuria or both?– Previous hypertensive pregnancies?

P/E:– Vitals ↑ BP.– In normal pregnancy, there’re substantial CV changes with a 50% ↑ in CO

& blood volume, which is accompanied by a ↓ in BP due to peripheral vasodilation. The changes in pre-eclampsia tend to be the reverse.

– Edema.– Funduscopic exam record baseline findings.

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Con’t (Dx)

For the purposes of clinical Dx & further evaluation, pts may be divided into 2 working groups:– Chronic HTN:

• Multiparous.• Those with previous Hx of HTN.• Those who developed HTN prior to 20wks gestation.

– Pre-eclampsia.• 1st pregnancy & develop syndrome after 20wks.

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Table 1. Initial lab evaluation of pt with pre-eclampsia / eclampsia

Blood Urine Other

CBC & Plt count: if ↓ Plts, ↓ Hb HELLP synd

Electrolytes: look @ BUN (may ↑) ↑ Uric acid.

Creatinine.LFT.

Sediment.24-hr protein.24-hr creatinine

(may ↓).

US.Test of fetal well-

being: NST. BPP. Cord color Doppler.

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Notes:

Serum uric acid correlates with poorer outcome for the mother & baby.Renal function is generally maintained in pre-eclampsia until late stage. If creatinine levels are high early in disease process, underlying renal disease should be suspected.In pre-eclampsia, Plt count ↓ due to increased consumption & intravascular destruction. Also, ↓ Plts is part of HELLP synd.Maternal Hb can be ↑ due to hypovolemia, and it’s a/w IUGR.Liver involvement:– Inflammatory infiltrates + obstructed blood flow in sinusoids

local welling subcapsular hemorrhage upper epigastric pain. ALT & AST leak across cell membranes (can also be a/w HELLP

synd).Additional lab test for chronic HTN may include ANA (for SLE) and ECG.

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Management

A. Outpatient observation:Use: only for transient HTN / uncomplicated chronic HTN.Specific guidelines:

a. Encourage left lateral rest to enhance placental perfusion.

b. Serially monitor mother watching for progression to pre-eclampsia / superimposed pre-

eclampsia. Check for BP, U-protein, headache, epigastric pain, scotomata.

c. Serially monitor fetus:• Non-stress test (NST), Amniotic Fluid Index (AFI), Biophysical profile

(BPP).

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Con’t (Mx)

B. Inpatient observation:Use: only for mild pre-eclampsia (< 36 weeks’ gestation).Specific guidelines:

a. Encourage left lateral rest to enhance placental perfusion.

b. Monitor mother & fetus watching for progression to severe pre-eclampsia or eclampsia.

c. Administer maternal steroids• = 2 doses of betamethasone IM 24 hours apart.

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Con’t (Mx)

C. Prompt delivery:Use: mild pre-eclampsia (≥ 36 weeks’ gestation), severe pre-eclampsia, eclampsia, chronic HTN with superimposed PIH, HELLP syndrome, or any evidence of maternal or fetal jeopardy.Specific guidelines:a. Lower BP:

keep diastolic value between 90-100 mm Hg.• = Use IV Hydralazine / IV Labetalol.

b. Prevent convulsions. Use IV MgSO4.c. Initiate delivery: Attempt induction of labor & vaginal delivery for 8-12

hours if mother & fetus are stable. Otherwise, perform C-section.

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Self-assessment

A 24-year-old gravida 1, para 0, at 37 weeks’ gestation was noted to have a 6-lb weight gain and an increase in blood pressure from 100/60 to 130/80 in the past week. She also has 1+ proteinuria. The examination was repeated 6 hours later and the same results were obtained. The best diagnosis is:

a. Normal pregnancy.b. Pre-eclampsia.c. Eclampsia.d. Chronic hypertension.e. Essential hypertension.

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Con’t (test)

The most common warning sign of pre-eclampsia is:

a. Proteinuria.b. Headache.c. Edema.d. Increased BP.e. Epigastric pain.

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Con’t (test)

The ultimate treatment for pre-eclampsia is:

a. Magnesium sulfate.b. Delivery.c. An antihypertensive drug.d. Renal dialysis.e. Bed rest.