High Blood Pressure in Pregnancy

High blood pressure, or hypertension, is a common complication in pregnancy. It is more common in women who are having their first baby, women with twins, those with high blood pressure before pregnancy and those with diabetes. It is important to recognize and manage hypertension as it can lead to problems for both the mother and the baby. You will have your blood pressure and urine protein checked at every visit with your care provider. Blood pressure problems in pregnancy usually develop towards the end of pregnancy and this is one of the reasons you are seen every week near the end of your pregnancy.

How will I know if I have high blood pressure in pregnancy?

High blood pressure in pregnancy is diagnosed by a blood pressure of over 140 systolic (top number) over 90 diastolic (bottom number).

Preeclampsia is a very serious condition that can happen in pregnancy. It is associated with high blood pressure and the spilling of protein into the urine. It can make both the mother and the baby very sick.

Symptoms of high blood pressure are nausea, a headache that won’t go away even with Tylenol, upper abdominal pain, and blurry vision or flashing lights in vision.

  • Blurred vision or flashing spots before your eyes
  • Headache that won’t go away even with the use of the usual medications such as Tylenol
  • Pain in your stomach area (just between your ribs)
  • Nausea 

If you have these symptoms, go to the Assessment Room right away!

What can happen to the mother if she has high blood pressure?

Rare but serious potential complications for the mother are seizure (eclampsia), stroke, liver injury, kidney injury or fluid in the lungs.

Risks for the mother

  • Seizures
  • Stroke
  • Liver injury
  • Kidney injury
  • Fluid in the lungs

What can happen to the baby if the mother has high blood pressure?

The baby may not grow or move as well, or the fluid around the baby can decrease. Very rarely, there might be a placental abruption (which is when the placenta separates from the uterus too soon) which can lead to distress or death of the baby.

Risks for the baby

  • Baby doesn’t grow as well
  • Baby doesn’t move as well
  • Decreased fluid around the baby
  • Premature delivery
  • Placental abruption
  • Fetal distress
  • Stillbirth 

What is the treatment for high blood pressure in pregnancy?

If you are still early in the pregnancy, your care provider may prescribe you medications to lower your blood pressure and your blood pressure will be closely monitored. You will have regular ultrasounds to follow the growth of the baby. You may need Celestone which is a medication that will help the baby’s lungs mature faster.

High blood pressure in pregnancy often slowly gets worse over time until the baby is delivered, so if you are close to your due date, the risks of waiting may outweigh the benefits, and the best option might be to induce labour and deliver the baby.

Management of high blood pressure

  • Blood pressure medication
  • Regular ultrasounds
  • Steroids to help baby’s lungs mature
  • Induction of labour
  • Delivery of baby

Is there anything I can do to prevent high blood pressure in pregnancy?

If you have high blood pressure or diabetes when you’re not pregnant, see you family doctor to help get the blood pressure and diabetes under good control before you try to conceive. You may also need to have your medications switched to ones that are safe in pregnancy. 

Try not to gain too much weight in pregnancy. 

There is some evidence that adequate calcium intake may reduce the chance of developing high blood pressure. If you had a previous pregnancy with high blood pressure or any of the complications associated with high blood pressure, your care provider may recommend taking baby aspirin in this pregnancy.

Prevention of high blood pressure

If high blood pressure in pregnancy is managed properly, usually mothers and babies do very well!

Learn more about preeclampsia and high blood pressure during pregnancy on the following websites: 
The American Congress of Obstetricians and Gynecologists.

UpToDate Patient Information 

Who benefits from taking a baby aspirin in pregnancy? 

  • High quality studies show that low-dose aspirin reduces the risk of severe high blood pressure in pregnancy, premature delivery, and underweight babies in women who are at higher risk.
  • These same studies show that low-dose aspirin is safe in pregnancy, with no harm to the fetus.
  • A woman should be identified as being at higher risk (or not at higher risk) by 12 to 16 weeks of pregnancy.

If a woman has any two of the following risk factors, then her pregnancy is said to be at relatively higher risk:

Factors in a previous pregnancy

  • Previous preeclampsia 
  • Previous placental abruption
  • Previous baby with low birth weight 
  • Previous delivery before 37 weeks 
  • Previous stillbirth

Factors in a current pregnancy

  • First baby
  • Age 40 years or older
  • Obesity (BMI over 30)
  • High blood pressure before pregnancy
  • Diabetes before pregnancy
  • Chronic kidney disease
  • Lupus
  • Use of infertility treatments
  • Twins or triplets

Aspirin 81 mg taken every night between 12-16 weeks to 36 weeks may reduce the risk of preeclampsia in high-risk women. 

Speak to your care provider about whether this medication is right for you.

If a woman has two or more of the above risk factors, then a baby aspirin 81 mg each night should be started at 12 to 16 weeks of pregnancy, as recommended by her doctor or midwife. If her caregiver feels that it is necessary, then aspirin may be started if there is a single very strong risk factor (e.g. chronic hypertension or chronic kidney disease), or three (3) weaker risk factors. The dose of aspirin should not be changed without a discussion with her pregnancy doctor or midwife. The aspirin can be continued until 36 weeks of pregnancy unless your doctor or midwife suggests a different time to stop it. 

Adapted from the research abstract Risk threshold for starting low dose aspirin in pregnancy to prevent preeclampsia: An opportunity at a low cost  

Abnormal placental markers 

When you do multiple marker screening to check for problems like Down syndrome and spina bifida, we check the levels of various biochemical markers such a PAPP-A, AFP, hCG and inhibin). When the results show that the risk for Down syndrome and spina bifida are low, but the individiual levels of the markers are either very low or very high, we think that this can be associated with risks such as a fetus that does gain weight well, early birth or an increased risk of the mother getting preeclampsia

Having abnormal markers alone is not very predictive of going on to develop a problem. Many women will go on to have uncomplicated pregnancies with healthy babies. Some women with abnormal markers, however, may go on to develop some of those problems described above. So how do we know who we should be worried about? 

Women are more likely to develop a problem later on in the pregnancy if they have abnormal markers in additional to risk factors for high blood pressure. You will also likely be sent for a placental scan between 22–26 weeks. This is a special ultrasound that checks to see how the placenta is working. A healthy placenta is flat and thin like a pancake. The cord is usually in the middle of the placenta and the blood flow from the uterus to the placenta (uterine artery) will be normal. 

If your placenta looks normal, then the chance of you going on to develop a problem will be low. If the placenta is bulky and shaped like a christmas pudding, with an umbilical cord that inserts on the edge of a placenta and a pattern of blood flow in the uterine artery called notching, then you are at a higher risk of developing a problem later in the pregnancy. 

Again, remember, not all women with these risk factors and abnormal placental scans will go on to have probems, but these risk factors warrant monitoring you and the baby closely with more frequent ultrasounds. Your care provider will review any risks and the plans specific to your case with you in more detail.

Placenta scan

  • Done between 22-26 weeks
  • Done for women with risk factors or abnormal biomarkers
  • Checks:
    •  shape of placenta — A shape like a pancake better than like a Christmas pudding
    •  umbilical cord insertion — In the middle of the placenta better than off to the side of the placenta 
    •  blood flow through from your body to placenta (uterine artery)
  • A woman with an abnormal placenta scan will be followed closely with regular ultrasounds

Learn about Mount Sinai Hospital’s Placenta Clinic. 

You must not rely on the information on this website as an alternative to medical advice from your doctor or other professional healthcare provider. If you have any specific questions about any medical matter you should consult your healthcare provider. If you think you may be suffering from any medical condition you should seek immediate medical attention. You should never delay seeking medical advice, disregard medical advice, or discontinue medical treatment because of information on this website.