What is pregnancy induced hypertension

Written by tanaypatel5212

May 18, 2021

 What is pregnancy-induced hypertension? All you should know about PIH

Pregnancy is the most precious time period for every mother and it is also one of the toughest periods for the mother. Today we will discuss what is pregnancy-induced hypertension in this article, before we start our article make sure you have some knowledge about what is blood pressure and its normal range in different age groups and gender.

List of topics in the article

  • What is blood pressure?
  • Definition of pregnancy-induced hypertension
  • Pathophysiology for pregnancy-induced hypertension

What is Blood pressure?

Blood pressure is the force of the circulating blood exerted on the walls of blood vessels.

It is different in different types of vessels, but the term “blood pressure“, when not specified otherwise, refers to the arterial pressure in the systemic circulation.

These are the 2 numbers on a blood pressure reading systolic and diastolic. We have discussed this in our previous articles.

If blood pressure rises above its normal value for a certain period it is defined as hypertension or high blood pressure.

And blood pressure falls from its normal value for a certain period of time it is defined as hypotension or low blood pressure.

What is pregnancy-induced hypertension?

Increase in Blood pressure more than 140 mm Hg of systolic and more than 90 mm Hg of diastolic pressure, on two occasions 4 to 6 hours apart.

Video courtesy:- Indian Medico (YouTube)

There are mainly two terms are used

  1. Pregnancy-induced hypertension (PIH)
  2. Chronic hypertension in pregnancy

If you find increased blood pressure during pregnancy then there are only two reasons which are mentioned above.

What is the difference between Pregnancy-induced hypertension and Chronic hypertension in pregnancy?

Pregnancy-induced hypertension: This is when there is a rise in blood pressure due to pregnancy after 20 weeks of gestation in a normotensive woman.

  • Here blood pressure comes to normal up to 12 weeks of delivery.


Chronic hypertension in pregnancy: Is mother has already been diagnosed with hypertension before pregnancy, and a rise in blood pressure during pregnancy due to previous hypertension history.

Here rise n blood pressure can be seen before 20 weeks and after 20 weeks also. Here blood pressure does not come to normal after delivery.

There is another condition that can develop which is known as chronic hypertension superimposed preeclampsia,

  • In this condition mother who has been already diagnosed with hypertension develops a severe rise in
  • Blood pressure dramatically around 160/110
  • Some time end-organ damage
  • Sudden onset of proteinuria.

What are pregnancy-induced hypertension disorders?

When we talk about Pregnancy-induced hypertension it is a very large term in itself, there is the various reason which affects the pregnancy and causes a rise in blood pressure.

So we can say that there is any defect in the pathophysiology of pregnancy that causes this condition called PIH. These conditions are

Gestataional hypertension

Here there is only a rise in blood pressure, there are no other signs and symptoms available in gestational hypertension

  • There is no proteinuria
  • No sign of end-organ damage


Preeclampsia is the stage before eclampsia, if pre-eclampsia develops and remains untreated or poorly treated then eclampsia develops. Signs and symptoms of pre-eclampsia include;

  • The rise in blood pressure
  • Along with proteinuriasa
  • Some time end-organ damage also seen


If pre-eclampsia remains untreated or poorly treated it causes a state of eclampsia, signs, and symptoms includes;

  • All the signs and symptoms of eclampsia
  • With fits of convulsion
  • Some time may result in a coma.

Criteria for proteinuria in pregnancy-induced hypertension

  • Excretion of 300 mg protein in 24 hours urine or,
  • 30mg/dl protein in the urine
  • or +ve dipstick test +1

Criteria or signs of end-organ damage in pregnancy-induced hypertension

  • Increase of platelet count < 1 lakh, It may be due to defect in cardiovascular system damage or defect in the blood system
  • Increase in creatinine of more than 1.1 mg/dl
  • Increase in liver enzyme in double of their normal value

Risk factors for pregnancy-induced hypertension.

  • Previous history of PIH
  • Primi gravida
  • Obesity
  • Maternal age either more than 40 or less than 20
  • Twins pregnancy, Triplets or quadruplets
  • Molar pregnancy
  • These are the most common risk factors in PIH

Etiopathogenesis of Pregnancy-induced hypertension

The most basic thing that we need to understand is a fetus inside the womb needs nutrition and a good blood supply. As the fetus grows day by day this requirement of blood supply also increases.

So this demand of blood supply and fulfillment of nutrition is managed by the placenta, any defect or any kind of problem to the placenta or in the placenta can cause the condition of PIH

Blood supply to the fetus is done by the process of trophoblastic invasion under the following conditions ;

  1. Low pressure,
  2. Low resistance,
  3. High volume.

If there is any defect in this process then it may cause severe illness to the mother and fetus also.

Any kind of defect in the trophoblastic invasion leads to a reduction in blood supply to the fetus and causes ischemia in the affected part of the placenta.

Whenever the ischemic changes occur it causes inflammation which leads to endothelial damage, this means there is damage that occurs to the endothelial capillaries. We know that capillaries have only one layer of cells and damage to the capillary endothelium makes pores in them.

Due to pore in capillary leakage of plasma occurs from inside to outside of the capillaries, so leakage of plasma along with blood leads to a low volume of blood in the circulatory system, this process is called capillary leaking.

Due to this leaking capillaries, the intravascular fluid goes into extracellular space results in edema which is most common in eclampsia and preeclampsia,

As plasma goes outside the capillaries hemoconcentration occurs which leads to a defect in platelet function and results further in thrombocytopenia, also a decrease in the volume of blood leads to poor blood supply to the end organs like the kidney, brain, lungs, and occipital lobe.

Effect on kidney:-

Poor blood supply to the kidney may cause the following effect on the urinary system;

  • Causes oliguria
  • Increase in creatinine
  • Proteinuria
  • If blood supply does not become normal it may cause kidney failure

Effect on the brain:-

Convulsion or seizures also called eclampsia

Effect on the lungs:-

If the blood supply of the lung is affected then it may cause pulmonary edema.

Effect on occipital lobe:-

Poor blood supply to the occipital lobe can lead to visual defects like blindness and other medical condition.

Prevention of Pregnancy-induced hypertension

Here we have to understand the predictors for PIH first before discussing prevention, certain changes occur during the pregnancy, and observation of these changes can help in the prevention.

The first predictor is uterine artery doppler 

Changes in uterine artery doppler are the most useful predictor for PIH. Normally before 24 weeks of pregnancy, there is a small notch after the peak notch in uterine doppler, and after 24 weeks of pregnancy, this notch starts becoming disappear gradually.

This small notch is called the diastolic notch and the peak notch is called the systolic notch. If the notch does not disappear after 24 weeks of pregnancy then it will be a predictor for PIH.

The concept behind this predictor is very simple, we all know that blood vessels are elastic in nature and they have one specific characteristic of impedance means they get recoil after every systole.

So after 24 weeks of pregnancy, the fetus becomes large in size and needs more blood supply and this done due to blood vessels gets relaxed and help to fulfill the requirement of blood so the notch disappears after the 24 weeks of pregnancy.

If the notch remains after 24 weeks it means that blood vessels are getting recoil and the pressure rises due to it, in PIH this occurs and leads to serious medical illness.

Medication to prevent pregnancy-induced hypertension

Aspirin is used for the prevention of PIH as it prevents thromboxane A2 which is prostaglandin, this causes prevention in vasospasm and helps to prevent it.

Also, a calcium diet and supplementation can help in the prevention of PIH.

Management of Pregnancy-induced hypertension

Now it is time to discuss the management of PIH. Management is divided into three main steps which are as follows ;

First step: Control of blood pressure

Control of blood pressure is very much important in the PIH, there are certain medicines which are helping to control blood pressure is

Labetalol is Beta-blocker and can help to control high blood pressure in pregnancy.

When to give?

When the blood pressure range is > 160/110 mm of Hg then labetalol is given in tablet form 100 mg BD/TDS.

If there is a hypertensive crisis means the blood pressure range goes much more than 160/110 again it should be given.

An IV bolus of Injection lobet 20 mg is given

If blood pressure does not control in 10 minutes 40 mg IV of injection lobet is given

If blood pressure is again not controlled in 10 minutes then 80 mg IV of injection lobet is given

If BP does not control by above these then continuous infusion of lobet can be done.

Second step: Prevention of eclampsia

In this step, we have to prevent the mother from going into the stage of eclampsia. The medicine of choice is MgSO4 (Magnesium sulfate)

Mechanism of action of magnesium sulfate

It stabilizes the central nervous system and prevents seizures, it also causes cerebral vasodilation and helps to prevent eclampsia.

There are two famous regimens for magnesium sulfate which are as follows

Pritchard regimen 

The total loading dose is 14 gm of MgSO4

In which 4 gm is given in IV

And 10 gm is given in IM

The maintenance dose is 5 gm of MgSO4 IM every 4 hours

Sibai regimen

In this 6 gm of MgSO4 IV which is loading dose in Sabai regimen

And 2 gm IV every 4 hours

Toxicity of MgSO4:

The main thing here we have to understand is the toxicity of magnesium sulfate, therapeutic range of MgSO4 in the body is 4-7mEq/L when its level increases > 7mEq/L it causes toxic effects in the body which are as follows ;

Signs of toxicity in the body and monitoring

Oliguria for which we have to monitor the urine output at least more than 30 ml/hr

The second is loss of deep tendon reflexes due to over stabilizing of synapses for this we have to go for a DTR test and it should be +ve

Respiratory depression may occur and we have to monitor respiratory rate which should be more than 14 or equal to 14 per minute and SPO2 should be more than 96


If magnesium causes a toxic effect then 10 ml of 10% calcium gluconate is given to antidote its effect.

Third step: Termination of pregnancy

As we discussed above the main and supreme cause for PIH is the placenta, so we have to remove the placenta if there is any serious medical illness occurs.

If there is mild preeclampsia then we can observe the symptoms and give treatment according to it and we only terminate the pregnancy if there is an urgent need of removing the pregnancy.

If there is severe preeclampsia then termination of pregnancy can be done at 34 weeks of pregnancy or early before 34 weeks.

In the cases of eclampsia

In these cases, termination of pregnancy is irrespective of age or gestational age. Also, we have to stabilize the patient.

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