What Causes Hypertension in Pregnancy?

Reviewed on 5/18/2021

Hypertension (high blood pressure) during pregnancy can potentially cause complications. Its cause is unknown, but risk factors include first-time pregnancy, previous preeclampsia, family history of preeclampsia, multiple pregnancy (twins, triplets, etc.), in vitro fertilization, type 1 or type 2 diabetes, obesity, chronic high blood pressure, chronic kidney disease, and others.
Hypertension (high blood pressure) during pregnancy can potentially cause complications. Its cause is unknown, but risk factors include first-time pregnancy, previous preeclampsia, family history of preeclampsia, multiple pregnancy (twins, triplets, etc.), in vitro fertilization, type 1 or type 2 diabetes, obesity, chronic high blood pressure, chronic kidney disease, and others.

Hypertension is the medical term for high blood pressure, which occurs when pressure in the arteries, the blood vessels that carry blood from the heart to the rest of the body, is higher than normal. 

  • Normal blood pressure is below 120/80
  • Blood pressure between 120/80 and 129/80 is elevated blood pressure
  • Blood pressure of 130/80 or above is considered high blood pressure

High blood pressure during pregnancy is common, and it occurs 1 in every 12 to 17 pregnancies among women aged 20 to 44 in the U.S.  If your blood pressure reading is high (140/90 or higher), especially after the 20th week of pregnancy, you may have a form of hypertension in pregnancy.

There are several types of high blood pressure that can occur during pregnancy: 

  • Chronic hypertension 
    • High blood pressure is present before a woman becomes pregnant or before 20 weeks of pregnancy
    • It is possible for women with chronic hypertension to also develop preeclampsia in the second or third trimester of pregnancy
  • Gestational hypertension
    • Refers to high blood pressure during pregnancy, without protein in the urine or other heart or kidney problems
    • Usually diagnosed after 20 weeks of pregnancy or close to delivery and tends to go away after delivery
    • Some women who develop gestational hypertension may have a higher risk of developing chronic hypertension in the future
  • Preeclampsia/eclampsia
    • Preeclampsia is a condition in which women who previously had normal blood pressure suddenly develop high blood pressure and protein in the urine or other problems after 20 weeks of pregnancy
    • Women with chronic hypertension can also get preeclampsia
    • Eclampsia is a medical emergency in which women with preeclampsia develop seizures
    • HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) is considered a subtype of preeclampsia with severe features
    • Postpartum preeclampsia is a rare condition and a medical emergency that occurs when women who did not have preeclampsia during pregnancy develop it after giving birth

It is unknown what causes hypertension during pregnancy. Risk factors for hypertension during pregnancy include: 

  • First-time pregnancy
  • Preeclampsia during a previous pregnancy
  • A family history of preeclampsia
  • Multiple pregnancy (twins, triplets, etc.)
  • Pregnancy occurred using in vitro fertilization
  • Type 1 or type 2 diabetes
  • Obesity
  • Chronic high blood pressure
  • Chronic kidney disease
  • A history of thrombophilia (a condition that increases risk of blood clots)
  • Being African-American
  • Age younger than 20 years or over 40 years 
  • Lupus 

What Are Symptoms of Hypertension During Pregnancy?

Hypertension (high blood pressure) usually doesn’t cause any symptoms. It is often dubbed “the silent killer” because many people don’t know they have high blood pressure until they develop a heart attack, kidney disease, or stroke.

Some pregnant women may have symptoms of hypertension, such as:

Not all women have symptoms of preeclampsia, but when symptoms occur, they may include:

  • Persistent headache 
  • Vision changes (blurred vision, seeing spots, or changes in eyesight)
  • Pain in the upper stomach area
  • Nausea or vomiting
  • Swelling of the face or hands
  • Sudden weight gain
  • Difficulty breathing

Hypertension during pregnancy doesn’t just affect the mother. High blood pressure can have the following effects on the unborn baby: 

  • Preterm delivery (premature birth that occurs before 37 weeks of pregnancy) 
  • Low birth weight (baby weighs less than 5 pounds, 8 ounces at birth)
  • Fetal growth restriction
    • High blood pressure in the mother can make it more difficult for the baby to get adequate oxygen and nutrients and it may grow more slowly
  • Fetal death
  • Neonatal death (death of the baby in the first 28 days of life)

How Is Hypertension During Pregnancy Diagnosed?

Hypertension (high blood pressure) is diagnosed using a pressure cuff (sphygmomanometer) to get a blood pressure reading. A cuff is placed around the upper arm and manually or electronically inflated. When inflated, the cuff compresses the brachial artery, the major blood vessel of the upper arm, briefly stopping blood flow. The air in the cuff is then released slowly while the person performing the measurement listens with a stethoscope or monitors an electronic readout.

Blood pressure is checked at prenatal visits. 

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What Is the Treatment for Hypertension During Pregnancy?

Treatment for chronic hypertension during pregnancy depends on how high the blood pressure is. 

  • In the first half of pregnancy, blood pressure normally drops and if the pressure is only mildly elevated, it may stay that way or return to normal during pregnancy
    • In this case, a doctor may recommend reducing or stopping blood pressure medication during pregnancy (never stop taking a prescribed medication without first talking to your doctor)
  • Severe hypertension or health problems associated with it may require starting or continuing blood pressure medication during pregnancy

Treatment for gestational hypertension depends on how close a woman is to her due date. 

  • When a woman is close to her due date and the baby is developed enough, delivering the baby as soon as possible may be advised
  • If hypertension is mild and the baby is not yet fully developed, lifestyle changes may be suggested: 
    • Resting, lying on the left side to take the weight of the baby off the major blood vessels
    • Reducing salt intake
    • Drinking 8 glasses of water each day
    • Increasing prenatal checkups
  • For severe hypertension, blood pressure medications may be prescribed until the woman is far enough along to safely deliver the baby

Treatment for mild preeclampsia may include: 

  • Blood pressure measurement at home
  • Monitoring fetal movement by doing a daily kick cunt
  • Visiting the ob-gyn once or twice weekly
  • Delivery may be considered at 37 weeks of pregnancy either by inducing labor with medications or via a cesarean birth (C-section)

Women who have severe preeclampsia may need to be treated in the hospital. 

  • For women at least 34 weeks pregnant, delivery may be considered once the mother’s condition is stable
  • Women less than 34 weeks pregnant and in stable condition may be able to wait to deliver the baby
    • Corticosteroids may be given to help the fetus’s lungs mature
    • Medications may be given to the mother to reduce blood pressure and help prevent seizures
    • Immediate delivery may be considered if the mother’s health or the fetus’s health worsens

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Reviewed on 5/18/2021
References
https://www.cdc.gov/bloodpressure/pregnancy.htm

https://www.acog.org/womens-health/faqs/preeclampsia-and-high-blood-pressure-during-pregnancy

https://americanpregnancy.org/healthy-pregnancy/pregnancy-complications/gestational-hypertension-859/