Hypertension in Pregnancy: Types, Causes & Treatment

What is pregnancy-induced hypertension, or hypertension in pregnancy?

Hypertension is increased in blood pressure (BP > 140/90) after 20 weeks of gestational age. It is essential to determine hypertension during pregnancy. However, it is a very serious complication during pregnancy. 10% of all pregnancies will have hypertension in pregnancy. Hypertension, which is before pregnancy, is known as chronic hypertension. Hypertension during pregnancy is known as gestational hypertension.

What are the different types of hypertension in pregnancy?

To understand types of hypertension during pregnancy, read the following points:

Gestational Hypertension

Gestational hypertension is very common during pregnancy. This is also known as transient hypertension. When blood pressure rises (BP > 140/90) after 20 weeks of pregnancy, then there is a chance of developing gestational hypertension. It doesn't have any other symptoms. Gestational hypertension goes its way after 12 weeks of delivery. However, it can increase the risk of high blood pressure in the future.

Preeclampsia

Preeclampsia is when BP is raised above the normal range, i.e., 160/110 or higher. Other symptoms include headache, stomach pain, nausea, vomiting, and vision change. It also usually develops after 20 weeks of pregnancy. It can lead to severe conditions for both the mother and baby, like organ failure and even death. 

Eclampsia

Convulsion (generalized tonic-clonic convulsions ) + Hypertension

It is the onset of convulsions (seizures) in pregnant women with preeclampsia.

Chronic Hypertension

Chronic hypertension is pre-existing hypertension present in early pregnancy. 

• New-onset proteinuria after 20 weeks
• Platelets <100,000/ul
• Creatinine >1.1 mg/dl
• Liver enzymes > two times normal

Acute on chronic Hypertension

Chronic hypertension patient with super-added gestational Hypertension

• New-onset proteinuria after 20 weeks
• Platelets <100,000/ul
• Creatinine >1.1 mg/dl
• Liver enzymes > two times normal

Delta hypertension

• There has been a sudden increase in mean arterial pressure.
• There is an increase in normal blood pressure throughout pregnancy.
• Later half high normal BP
• May have proteinuria, convulsions

To understand gestational hypertension step by step according to the previous types and their severity. Read the following points carefully.

Gestational hypertension

↓

Preeclampsia

↓

Eclampsia

↓

Hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome)

↓

Worsening KFT, pulmonary edema, cortical venous thrombosis, DIC

↓

It can lead to the death of the patient.

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How to understand imminent eclampsia/worsening HTN?

Stage before the eclampsia: following symptoms Patient will have

• Headache
• Nausea
• Vomiting
• Blurring
• Exaggerated knee reflex
• Epigastric pain: Subcapsular hematoma of liver
• Falling platelets: Platelet aggregation
• Raised liver enzymes
• Deranged kidney function
• Pulmonary edema
• Proteinuria >2g/24 hours
• Diastolic BP >110 mm Hg

Treatment of eclampsia

• DOC to prevent convulsion: MgSO4
• DOC to decrease BP: IV labetalol
• Terminate the pregnancy

What is placental perfusion?

• Placental perfusion refers to the blood flow between the mother and the fetus through the placenta. The villi of the baby into the blood from the spiral artery of the mother: Nourishes the baby. At 20 weeks of gestation, extravillous trophoblasts will move into the uterus stroma and into the smooth muscle layer of the spiral artery and replace it. Then it is known as endovascular extravillous trophoblast.

• In the 3 trimester: The entire muscle layer of the spiral artery is replaced by extravillous

trophoblasts and the vessel is well dilated and gives good blood into the pool where the villi are inserted At 20 weeks, this process is known as secondary placentation.

• Primary placentation: At six weeks of pregnancy, the placenta takes over the function of maintenance of pregnancy (luteoplacental shift takes place). 

• If the invasion of trophoblasts is inadequate: It will lead to the persistence of primitive vasculature, Vasospasm results in the spiral arteries

Also read: IVF & OHSS Explained: Risks, Symptoms, and Treatments

Etiopathogenesis/The causes and development of HIP 

Stage 1: Poor placentation

Role of Immune Factors in Poor Placentation

• T-helper 1 cells mediate secretion of inflammatory cytokines like
  • TNF-α
  • γ-interferon
  • IL-2
  • These form macrophages and NK cells, which work against intracellular pathogens

• T-helper 2 cells: Humoral immunity
• In normal pregnancy: T-helper 2 bias
• In preeclampsia: T-helper 1 cell function increases
  •  Causes deficient vascular modification
  •  Results in vasospasm

Stage 2: Maternal syndrome

Endothelial activation: Causing vasospasm

• Increase in vasopressors
  • Angiotensin II
  • Thromboxane A2
  • Endothelin I
• Reduction in vasodilators
  • PGI2 (prostacyclin), Nitric oxide
  • PGI2 and TXA2 ratio are reduced

Imbalance between angiogenic and antiangiogenic factors

These factors result in poor placentation, vasospasm, and endothelial activation.

Presents after 20 weeks with increased blood pressure of more than 140/90 mmHg

• Angiogenic factors: Reduced
  • Vascular Endothelial Growth Factor (VEGF)
  • Transforming Growth Factor (TGF)
  • Platelet-like  Growth Factor (PLGF)

• Antiangiogenic factors: Increased
  • Soluble fms like tyrosine kinase-1: Inactivates VEGF and PLGF
  • Increase in soluble endoglin: Inhibits TGF

Normally, Transforming Growth Factor (TGF) and Vascular Endothelial Growth Factor (VEGF) bind to the receptors in the blood vessel, resulting in vasodilation.

In preeclampsia

• Soluble endoglin will bind to the Transforming Growth Factor (TGF),Not allowing it to bind to the receptors on the blood vessels. 
• Soluble fms like tyrosine kinase-1 will bind to the Vascular Endothelial Growth Factor (VEGF), Not allowing it to bind to the receptors on the blood vessels

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Pathology 

Main pathology is Vasospasm

Hemolysis: Due to endothelial activation results in 

• Anemia
• Increase in LDH
• Reduced haptoglobin - Binds to free hemoglobin
• Schistocytosis - Broken RBCs

Liver

• Transaminitis: Elevated enzymes
• Periportal hemorrhage: Subcapsular hematoma

Due to acinar damage

• Causes: epigastric pain
• Remember: Liver function is essentially normal

CNS

• Microscopy: fibrinogen necrosis + Perivascular microinfarcts
  • If seen in the frontal cortex: Headache
  • If seen in the occipital cortex: Scotoma or blindness
• Cortical and subcortical petechiae
• Intra-cerebellar hemorrhage
• Release of glutamic acid: Excitatory neurotransmitter
  • Reason for convulsions

Kidney

• Normal pregnancy: increase in GFR and renal blood flow
• Hypertension in pregnancy: Reduced GFR and RBF, This is due to an increase in renal afferent arteriolar resistance
• Glomerular capillary endotheliosis: blocks filtration

Also read: Pre Conception and Prenatal Diagnostic Techniques (PCPNDT)

What is HELLP syndrome?

Full form of HELLP syndrome:

Hemolysis is the breakdown of RBCs

EL: Elevated liver enzymes: Indicated liver damage

LP (low platelets): bleeding problem

HELLP syndrome is a rare but very serious complication of pregnancy. It affects the liver and blood cells. 

Hemolysis

• Burr cells
• Schistocytes
• Bilirubin ≥ 1.2 mg/dl
• Low haptoglobin
• LDH ≥ twice the upper normal limit (>600 U/L)

Elevated liver enzymes

• Elevated AST & ALT ≥ twice the upper normal limit 72 U/L

Low platelets: <1,00,000/cu.mm

Treatment for hypertension in pregnancy

Gestational HTN

Can be managed by

• Home BP charting
• Antihypertensives

Preeclampsia

• Always admit the patient and evaluate Peripheral blood smear, Clotting profile and liver enzymes
• Steroids if < 34 weeks
• Maternal surveillance: 4 hourly BP, Weight gain, Urine R/M, Uric acid, Creatinine, LFT, LDH and Coagulation profile
• Fetal surveillance
• Check FMS like TK-1 and PLGF

Also read: Forensic Psychiatry : Mental Health Care Act

Which drugs are used to treat hypertension in pregnancy?

Labetalol

• 1st line drug
• Drug of choice in gestational or chronic HTN
• Alpha + Non-selective beta blocker
• Does not cause:
  •  Headache
  •  Hypotension
  •  Tachycardia
  •  Reduction of uteroplacental flow

• Contraindication: Asthmatics
• Dose: 100-200 mg/day TID up to 2400 mg/24 hrs

Hydralazine

• Dose: 24 to 50 mg OD or BD up to 200 mg/day
• Arteriolar dilator (No action on veins)
• IV dose: 5 to 10 mg
• Acetylated in the liver: Slow acetylators are given reduced dose
• Side effects: Lupus-like syndrome, Headache, hypotension and tachycardia

Methyldopa

• Is a product?
• Drug of choice after labetalol
• Active form: α-methyl norepinephrine
• Dose: 250 to 500 mg QID—starts action in 48 hours
• Side effects: Drowsiness, Depression and False positive ICT

Nifedipine

• Calcium channel blocker
• Dose: 5-10 mg TID-QID up to 90 mg/day
• Side effects: Flushing and headache
• Avoid giving sublingual - Causes sudden hypotension

Prazosin

• Alpha blocker
• Acts only on capacitance vessels like veins
• Dose: 2-4 mg daily
• It causes a rapid reduction of BP
• Side effects: Hypotension

Contraindicated drugs

• Furosemide reduces the perfusion in the placenta further and causes IUGR
• Beta-blockers cause intrauterine growth restriction (IUGR)
• ACE inhibitors: causes:
  • IUGR
  • Hypocalvaria
  • Limb contractures
  • Renal agenesis
  • Oligoamnios

How to control blood pressure (BP) in eclampsia? 

• IV labetalol 20 mg—can be doubled for every 20 minutes
• No control in BP: 20-40 mg is given after 20 minutes
• Still no control in BP: 80 mg is given after 20 minutes
• Can be used up to 220 mg IV to control BP

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Prevention 

• Control diseases like DM and renal disease
• Avoid pregnancy in young girls and elderly gravidas
• Knowledge of pathophysiology
• Low-dose aspirin: 75-150 mg/day (Reduce the platelet production of thromboxane)
• Calcium supplementation: Reduce the intracellular calcium levels reduce membrane excitability and reduce smooth muscle contractility
• Omega 3 fatty acids (in fish oil): Competes with arachidonic acid in platelets (Lesser production of thromboxanes)
• Antioxidants: Vitamin C and E

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