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Your blood pressure is monitored throughout pregnancy; you should expect your doctor or midwife to check it at every prenatal visit. Perhaps you’ve been told that yours is running high or low and are worried about what this means. Or maybe you’re just curious about the changes that are happening in your body right now and interested in learning all you can about how the systems in your body are working together to create your little miracle.
Table of contents
About Blood Pressure
What is blood pressure?
Blood pressure is the force of the blood pressing against the walls of the arteries as the heart beats (1). Each time your heart contracts, or squeezes, it pushes blood into your vessels and pressure in the vessels increases. Between your heart’s beats, the pressure drops.
Systolic vs diastolic
When your healthcare provider checks your blood pressure, she records it as two numbers. The top number is called the systolic pressure, which is the pressure when your heart beats. The bottom number is the diastolic pressure, which is how much pressure is in your veins when your heart is relaxed between beats (1, 2).
What the numbers mean
Your blood pressure is considered “normal” if your systolic pressure (top number) is less than 120 and your diastolic pressure (bottom number) is less than 80. High blood pressure, also called hypertension, is when your systolic pressure is over 140 and/or your diastolic pressure is over 90 (2). If your pressure runs between these numbers, it is considered elevated or as stage 1 hypertension, and your doctor will want to keep an eye on it.
High Blood Pressure Pregnancy
Some women have high blood pressure before pregnancy. If your blood pressure is high before you become pregnant, or during the first 20 weeks of pregnancy, this is classified as chronic hypertension. This condition is not expected to go away during pregnancy; you and your healthcare provider will work together to manage it (3). If your blood pressure starts running high after the 20th week of pregnancy, this is classified as gestational hypertension, which usually goes away after your baby is delivered.
Your doctor or midwife will check your blood pressure at each prenatal appointment. One high reading isn’t cause for alarm, as blood pressure fluctuates. But if your readings are elevated several times, you will be diagnosed with hypertension. Don’t panic. This is a common condition which occurs in one of every twelve to seventeen pregnancies, and your caregiver will know how to help you manage it.
While not necessarily a cause for great concern, there are some risks associated with high blood pressure during pregnancy. Some of these risks are the same as in non-pregnant people, like a greater chance of having a heart attack or stroke, and damage to organs over time which can result in things like kidney failure. There are also risks that are specific to hypertension during pregnancy. These pregnancy-specific risks include:
- Increased chance of preeclampsia and eclampsia
- A need for induced labor or cesarean section
- Placental abruption (the placenta separating from the uterus)
- Pulmonary edema
- IUGR (intrauterine growth restriction) which is when the baby grows too slowly as a result of not getting enough oxygen or nutrients
- Low birth weight
- Premature delivery
- Slight increased risk of stillbirth (1, 4, 5)
Managing High Blood Pressure
If you have high blood pressure before pregnancy, and you take medication for it, talk to your doctor or midwife about whether it’s safe to continue taking it. Most blood pressure medications are considered safe for pregnancy, but you should avoid ACE inhibitors (3). In some cases, women are able to stop taking their medication because their blood pressure may come down during pregnancy. (This is due to the fact that pregnancy hormones make your blood vessels relax/dilate when you’re pregnant.) If your doctor tells you to continue your medicine, or if you start one during pregnancy, make sure you take it every day as prescribed.
If you have hypertension in your pregnancy, you may have more ultrasounds so that your baby’s growth can be monitored more closely. You may be asked to check your blood pressure at home between prenatal visits. Like all pregnant women, you should choose healthy foods, but particularly make sure not to eat foods that are high in sodium (salt). Stay active, aiming for 30 minutes of activity each day. Try to decrease the stress in your life, as stress can raise blood pressure.
Low Blood Pressure Pregnancy
Low blood pressure (less than 90/60) is common during pregnancy, especially in the first two trimesters. Hormones cause your blood vessels to dilate to accommodate the increased blood volume needed to support your baby, causing blood pressure to run lower. Things like dehydration and anemia that can be caused by morning sickness can also contribute to lower blood pressure.
Low blood pressure doesn’t typically cause any problems and doesn’t require treatment. Your pressure will likely begin to rise during the third trimester, and if not, should return to normal after your baby is born. If low blood pressure causes you to feel dizzy, as it sometimes can, here are some things that you may find helpful:
- Don’t stand up too quickly from a seated or lying position
- Drink plenty of water
- Don’t take hot baths or showers (long, hot baths or showers are not recommended during pregnancy anyway, so as not to raise your body temperature too much)
- Don’t stand for long periods of time
- Eat small meals throughout the day
When To Call The Doctor
The biggest risk associated with blood pressure during pregnancy is preeclampsia. This is a condition when a woman, after the 20th week of pregnancy, has high blood pressure and signs that some of her organs may not be working normally. Most of the time, even in a pregnancy where the mom develops preeclampsia, babies are born healthy. But there is the potential for very serious side effects, including the mother or baby’s death, so it must be managed carefully.
Call your doctor right away if you have any of these preeclampsia symptoms:
- Changes in vision like blurriness, flashing lights, seeing spots, or being sensitive to light
- Headache that doesn’t go away
- Nausea, vomiting or dizziness
- Pain in the upper right belly area or in the shoulder
- Sudden weight gain (2 to 5 pounds in a week)
- Swelling in the legs, hands or face
- Trouble breathing (6)
Some of these are normal pregnancy discomforts, but it’s better to be safe with a call to your doctor if you experience any of them.
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- High blood pressure during pregnancy. (2019, February). Retrieved November 30, 2020, from https://www.marchofdimes.org/complications/high-blood-pressure-during-pregnancy.aspx
- The American College of Obstetricians and Gynecologists. (2010). Your Pregnancy and Childbirth Month to Month, 5th edition
- Glade, B.C., Schuler, J. (2011). Your Pregnancy Week by Week, 7th edition. First Da Capo Press
- High Blood Pressure During Pregnancy. (2020, January 28). Retrieved November 30, 2020, from https://www.cdc.gov/bloodpressure/pregnancy.htm
- Barratt, J., Cross, C., Steel, S., & Biswas, C. (2016). The pregnancy encyclopedia: All your questions answered. London: Dorling Kindersley Limited.
- Preeclampsia. (2020, October). Retrieved November 30, 2020, from https://www.marchofdimes.org/complications/preeclampsia.aspx