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2 September 2021

Blood Pressure Changes in Pregnancy

Pregnancy can impact your blood pressure in different ways. Often it can cause blood pressure to drop, which doesn’t usually cause problems. When blood pressure increases in pregnancy though, this can lead to serious complications for both mum and baby.

pregnancy test

How will my blood pressure change in pregnancy?

Your circulatory system grows rapidly when you’re carrying a baby, which can cause a decrease in blood pressure. This is typically something that your midwife will do at every encounter as a minimum. You may require extra monitoring depending on your readings.

During the first 24 weeks of pregnancy, it’s typical for your blood pressure to drop.

How is my blood pressure measured?

A device called a sphygmomanometer (blood pressure machine) will be used to take your blood pressure readings.

It may be done automatically with a digital machine, or manually, which involves a stethoscope, arm cuff, pump, and dial are generally included, however, automated systems with sensors and a digital display are very prevalent nowadays.

When taking a blood pressure reading, it’s recommended to sit with your back supported and your legs uncrossed. To fit the cuff over your upper arm, you’ll need to roll up your sleeves or remove any long-sleeved clothes. While the test is being performed, try to relax and avoid chatting.

Once your blood pressure has been taken you will be given two numbers:

The systolic reading gives the pressure of your blood on your arteries as it travels around your body when your heart contracts. An ideal systolic reading would be 120 but this depends on your pre-pregnancy blood pressure as an increase from your baseline reading can be significant even if it is lower than this.

The diastolic reading is the lowest pressure on your arteries when your heart rests between beats. An ideal diastolic reading would be 80, again depending on your baseline.

Why is my blood pressure measured?

Blood pressure refers to the force with which your blood pushes against the sidewalls of your arteries as it circulates throughout your body.

Hypertension (high blood pressure) puts a burden on your arteries and organs, increasing your risk of catastrophic issues including heart attacks and strokes. It can be particularly dangerous in pregnancy, both for mum and baby.


Although low blood pressure (hypotension) can induce dizziness and fainting in some people, it is typically not as dangerous.

If you’ve been taking blood pressure medication throughout your pregnancy, continue to do so throughout labour.

Your blood pressure should be checked hourly during labour if you have mild or moderate hypertension. You should be able to have a natural vaginal delivery as long as your blood pressure is within goal ranges.

Your blood pressure will be checked every 15 to 30 minutes throughout labour if you have severe hypertension. Your doctor may also suggest delivering your baby by forceps, ventouse, or caesarean section.

Your blood pressure will be checked after the birth.

If you had hypertension before becoming pregnant, you should have your medication reviewed two weeks after your baby is born.

Sometimes blood-pressure related issues can develop even after giving birth so continue to be vigilant and seek medical attention if you have any symptoms or concerns about this.

Causes of abnormal blood pressure during pregnancy

There are several possible causes of high blood pressure during pregnancy.

These include:

  • being overweight or obese
  • not getting enough physical activity
  • smoking
  • drinking alcohol
  • a family history of pregnancy-related hypertension
  • carrying more than one child
  • age (over 35)
  • having diabetes or certain autoimmune diseases

Obesity and other common risk factors for high blood pressure can be reduced via diet and exercise. Please speak to your midwife or GP about how to lose weight safely during pregnancy.

Dietary recommendations for pregnant women differ from one person to the next. A nutritionist may assist you in developing a food plan that is tailored to your height and weight.

Avoid smoking and consuming alcoholic beverages. Both are known to increase blood pressure and induce other pregnancy problems.

Salt is essential during pregnancy, and limiting salt consumption is typically unnecessary, even for women with high blood pressure. Excessive salt restriction can damage pregnant women and have an influence on foetal growth and development.

Hormone changes, as well as psychological and physical changes, occur throughout pregnancy. This can cause tension, which makes it more difficult to control high blood pressure. Try stress-relieving exercises like yoga and meditation.

Medication for high blood pressure during pregnancy

Some traditional blood pressure medications can cause problems in pregnant women.

These medications for lowering blood pressure are typically not recommended during pregnancy:

  • ACE inhibitors
  • angiotensin receptor blockers

These drugs will pass through the bloodstream to the baby and negatively impact the developing baby’s health.

Methyldopa and labetalol are both drugs that are considered safe to use to manage blood pressure during pregnancy.

Complications of abnormal blood pressure during pregnancy

If chronic high blood pressure is not managed during pregnancy, it can be harmful and even fatal to both the mother and the foetus.

According to the latest UK maternal report, heart disease is still the leading cause of maternal death in the country. This in itself is often linked to abnormal blood pressure, so any symptoms or concerns should be discussed promptly with your midwife or doctor.

In general, diligent monitoring and some lifestyle modifications can reduce your risk of high blood pressure problems.

Of course, high blood pressure can also be linked with preeclampsia and eclampsia.

Preventing abnormal blood pressure during pregnancy

Keeping active and engaging in some form of physical exercise each day, such as walking or swimming, can help you maintain healthy blood pressure levels. Blood pressure can be lowered by eating a well-balanced diet.

There isn’t enough data to suggest that taking dietary supplements like magnesium, folic acid, or fish oils will help prevent high blood pressure. Any supplements that you are interested in taking that are not recommended by the NHS should be discussed with your midwife or doctor first, as they may pose additional risks in pregnancy.

What are the different types of high blood pressure?

Chronic Hypertension

By this, we mean already being diagnosed with hypertension prior to becoming pregnant. Hypertension, or high blood pressure, raises the risk of coronary heart disease (heart attack) and stroke (brain attack). High blood pressure usually has no warning signs or symptoms. You can find out whether your blood pressure is high by getting it tested by your doctor or at home on a regular basis.

Gestational Hypertension

Gestational hypertension is high blood pressure in pregnancy. It occurs in about 3 in 50 pregnancies.

It’s different from preeclampsia and eclampsia, but it can lead to these developing – more on these later in this article.

This issue often starts in the second half of pregnancy. It normally goes away a number of weeks after your baby is born.

Dangers of high blood pressure during pregnancy


What is preeclampsia?

Preeclampsia is essentially when the blood pressure increases during pregnancy, and there is also protein loss in the urine.

It is a serious condition as it can lead to growth restriction of the baby, pre-term delivery, severe breathing problems in the baby, and can be life-threatening for both mum and baby. It can also progress to eclampsia (covered later) or be associated with a serious condition called HELLP Syndrome:

  • Haemolysis (blood cells breaking apart)
  • Elevated Liver enzymes (a sign of liver damage)
  • Low Platelets (can cause dangerous bleeding)

Who is at risk for preeclampsia?

You are more at risk for preeclampsia if:

  • You are giving birth for the first time.
  • You have a history of preeclampsia from a prior pregnancy.
  • You have high blood pressure that has been present for a long time, or you have chronic renal disease, or both.
  • You’re expecting numerous children (such as twins or triplets).
  • You have a history of preeclampsia in your family.
  • You have diabetes, either type 1 or type 2.
  • You’re overweight. (Body Mass Index of 35 or more)
  • You’ve been diagnosed with lupus (an autoimmune disease).
  • You are over the age of 40.

What are the symptoms of preeclampsia?

Symptoms of preeclampsia include:

  • A headache that will not go away
  • Changes in vision, including blurry vision, seeing spots, or having changes in eyesight
  • Pain in the upper stomach area
  • Nausea or vomiting
  • Swelling of the face or hands
  • Sudden weight gain
  • Trouble breathing

Some women have no symptoms of preeclampsia, which is why it is important to keep your regular appointments with your health care team, especially during pregnancy.

How is preeclampsia diagnosed?

Pre-eclampsia is easily diagnosed during the routine checks you have while you’re pregnant.

During these antenatal appointments, your blood pressure is regularly checked and a urine sample is tested to see if it contains protein.

If you notice any of the symptoms of pre-eclampsia between your antenatal appointments, see your midwife or GP for advice promptly, as this can potentially be a medical emergency.

What are the treatments for preeclampsia?

Pre-eclampsia can only be cured by delivering the baby. If you have pre-eclampsia, you’ll be closely monitored until it’s possible to deliver the baby.

Once diagnosed, you’ll be referred to a hospital specialist for further assessment and any necessary treatment.

If you only have high blood pressure without any signs of pre-eclampsia, you can usually return home afterwards and attend regular (possibly daily) follow-up appointments.

If pre-eclampsia is confirmed, you’ll usually need to stay in hospital until your baby can be delivered.

What about after giving birth?

Preeclampsia can occur after you’ve given birth in rare circumstances. Postpartum preeclampsia is a severe medical disease that occurs after a woman gives birth. It can happen to women who have never had preeclampsia throughout their pregnancy.  Postpartum preeclampsia shares many of the same symptoms as preeclampsia. Preeclampsia after birth is usually identified within 48 hours, although it can occur up to 6 weeks later. 


Eclampsia is a serious preeclampsia consequence. High blood pressure causes life-threatening, non-stop seizures during pregnancy, which is an uncommon but dangerous disease.

Seizures are moments of abnormal brain activity that can result in staring, drowsiness, and convulsions (violent shaking). Eclampsia affects around one out of every 200 women who have preeclampsia. Even if you don’t have a history of seizures, you can develop eclampsia.

It can also be associated with stroke, placental abruption (where the placenta starts to detach from the womb) and HELLP Syndrome.


What should I do if I have low blood pressure before, during, or after pregnancy?

Before pregnancy

Speak to your GP or specialist if you are known to have low blood pressure and are planning on trying to conceive, especially if you are taking any medication for this.

During pregnancy

It’s common for your blood pressure to lower in the first 24 weeks of pregnancy.

Other factors that can contribute to low blood pressure include:

  • dehydration
  • internal bleeding
  • prolonged bed rest
  • certain medications
  • heart conditions
  • endocrine disorders
  • kidney disorders
  • infections
  • nutritional deficiencies

After pregnancy

After you give delivery, your blood pressure should recover to pre-pregnancy levels.

In the hours and days following your baby’s birth, medical personnel will check your blood pressure often. Additionally, during your postnatal office visits, your doctor will most likely check your blood pressure.

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