High blood pressure, or hypertension, is defined as blood pressure higher than 140/90 mm Hg. The condition is a serious concern for some pregnant women.
High blood pressure during pregnancy isn’t always dangerous. But it can sometimes cause severe health complications for both mother and developing baby. According to the Centers for Disease Control and Prevention, an increasing number of pregnant women in the United States have this condition.
According to the National Heart, Lung, and Blood Institute (NHLBI), there are several possible causes of high blood pressure during pregnancy.
- being overweight or obese
- failing to stay active
- drinking alcohol
- first-time pregnancy
- a family history of pregnancy-related hypertension
- carrying more than one child
- age (over 40)
- assistive technology (such as IVF)
Unhealthy lifestyle choices may lead to high blood pressure during pregnancy. Being overweight or obese, or not staying active, are major risk factors for high blood pressure.
Women experiencing their first pregnancy are more likely to have high blood pressure. Fortunately, there’s a lower chance of this condition in subsequent pregnancies with the same partner.
Maternal age is also a factor, with pregnant women over the age of 40 being more at risk.
According to the American Society for Reproductive Medicine, using assistive technologies (such as IVF) during the conception process can increase chances of high blood pressure in a pregnant woman.
Women who had high blood pressure before pregnancy are at higher risk for related complications during pregnancy than those with normal blood pressure.
- Chronic hypertension: Sometimes a woman has pre-existing high blood pressure, or hypertension before she gets pregnant. This may be referred to as chronic hypertension, and is usually treated with blood pressure medication. Doctors also consider hypertension that occurs in the first 20 weeks of pregnancy to be chronic hypertension.
- Gestational hypertension: Gestational hypertension develops after the 20th week of pregnancy. It usually resolves after delivery and the most common complication is induced labor. When diagnosed before 30 weeks, there’s a higher chance it will progress to preeclampsia (see below).
- Chronic hypertension with superimposed preeclampsia: Another variation of chronic hypertension is when a woman has hypertension before she becomes pregnant, then also experiences protein in her urine or additional complications as her pregnancy progresses.
A blood pressure reading is a fraction: your systolic blood pressure over your diastolic blood pressure.
- The top number is your systolic pressure, which is a measurement of the pressure on your heart’s arteries when the heart is beating or squeezing blood forward through your body.
- The diastolic or lower number is a measurement of the force of blood pressure in your heart when the heart is at rest.
What is considered normal blood pressure during pregnancy?
To determine what your “normal” blood pressure is during pregnancy, your doctor will likely take a baseline blood pressure measurement at your first visit. Then they will measure your blood pressure at every visit that follows.
Normal blood pressure is usually somewhere close to 120/80 mm Hg.
What is considered high blood pressure during pregnancy?
A blood pressure that is greater than 140/90 mm Hg, or that is 15 degrees higher on the top number from where you started out before pregnancy, may be cause for concern.
Early in pregnancy, usually from 5 weeks’ pregnant to the middle of the second trimester, a pregnant woman’s blood pressure may actually decrease. This is because pregnancy hormones can stimulate blood vessels to widen. As a result, the resistance to blood flow isn’t as high.
What is considered low blood pressure during pregnancy?
While there isn’t a definitive number that is too low, there are symptoms that are associated with low blood pressure:
As a woman progresses in her pregnancy, her blood pressure may change or return to prepregnancy levels. Reasons for this may include the following.
The amount of blood in a woman’s body increases. According to the journal Circulation, a woman’s blood volume increases by as much as 45 percent during pregnancy. This is an extra amount of blood that the heart must pump throughout the body.
The left ventricle (left side of the heart that does a significant amount of pumping) becomes thicker and larger. This temporary effect allows the heart to work harder to support the increased blood volume.
The kidneys release increased amounts of vasopressin, a hormone that leads to increased water retention.
In most cases, high blood pressure during pregnancy will subside almost immediately after the baby is delivered. In cases where blood pressure remains elevated, your doctor may prescribe medication to get it back to normal.
Tips for tracking blood pressure during pregnancy
There are many ways that you can track your blood pressure during pregnancy. Try out the following ideas:
- Purchase a blood pressure monitor from a pharmacy or online medical goods store. Many of these devices will go on your wrist or upper arm. To ensure that the monitor is accurate, take it to your doctor’s office and compare the readings on the monitor to those from your doctor.
- Visit a grocery store, pharmacy, or other store that has a machine that takes blood pressure readings.
- For the most accurate readings, take your blood pressure at the same time every day. Take it while seated with your legs uncrossed. Use the same arm each time.
- Notify your doctor immediately if you have repeated high blood pressure readings that are four hours apart, or symptoms of high blood pressure.
If high blood pressure continues after 20 weeks of pregnancy, there can be complications. Preeclampsia can develop.
What is preeclampsia?
This condition can cause serious damage to your organs, including your brain and kidneys. Preeclampsia is also known as toxemia or pregnancy-induced hypertension. Preeclampsia with seizures becomes eclampsia. This can be fatal.
Thorough prenatal care, including regular doctor’s visits, should be able to address preeclampsia symptoms. Symptoms include:
- protein in a urine sample
- abnormal swelling in hands and feet
- persistent headaches
HELLP is an acronym that stands for hemolysis, elevated liver enzymes, and low platelet count. This condition is severe and life-threatening, and can be a complication of preeclampsia. Symptoms associated with HELLP include nausea, vomiting, headache, and upper abdominal pain. Because HELLP syndrome can severely damage organ systems vital to life, emergency medical care is aimed at reducing blood pressure for the health of the mother and the baby. In some cases, a premature delivery is required.
High blood pressure during pregnancy can also have an effect on the baby’s growth rate. This can result in low birth weight. According to the American Congress of Obstetricians and Gynecologists, other complications include:
- placental abruption, a medical emergency during which the placenta detaches from the uterus prematurely
- preterm delivery, defined as delivery prior to 38 weeks of pregnancy
- caesarean delivery
Common risk factors for high blood pressure, such as obesity and a history of high blood pressure, can be minimized through diet and exercise. Of course, during pregnancy, it is inevitable that you will gain some weight. It’s recommended that pregnant women consult with their doctor to identify a weight gain target that is healthy for them.
Dietary guidelines for pregnant women vary from person to person. Speak with a nutritionist who will keep your specific height and weight in mind when creating a nutrition plan for you.
The NHLBI emphasizes that it’s important to take steps to lessen your risk of high blood pressure. You should steer clear of smoking and drinking alcohol, both of which have been known to raise blood pressure.
Pregnancy causes hormone shifts, as well as psychological and physical changes. This can bring on stress, which can make high blood pressure harder to manage. Try stress reduction techniques such as yoga and meditation.
Some traditional blood pressure medications can cause problems in pregnant women.
According to Mayo Clinic, these medications for lowering blood pressure should be avoided when you are pregnant:
These drugs in particular will be passed through the bloodstream to the developing baby. They can negatively impact the baby’s health. These medications may also cause blood to thin, which can compromise the mother’s ability to carry the baby to term.
Methyldopa and labetalol are both drugs that have been deemed safe for use to manage blood pressure during pregnancy.
Talk to your doctor about how to control your blood pressure if you develop hypertension during pregnancy.
High blood pressure during pregnancy doesn’t usually lead to serious problems. However, if it goes untreated, hypertension can become life-threatening for both mother and baby. Unfortunately, hypertensive disorders resulting from high blood pressure are the second-leading cause of U.S. maternal death during pregnancy.
Always talk to your doctor about your concerns. Plan to stay on top of your prenatal care to have the healthiest pregnancy outcome possible.
Take the time to understand the risk factors and possible causes of high blood pressure before you get pregnant — and take preventive measures to keep your blood pressure down during pregnancy.