Blood pressure 101: What every pregnant mom needs to know
Quick Overview
In this blog, you'll get key insights on managing blood pressure during pregnancy, from understanding what affects it to learning how to track your baseline. With practical tips and information, you'll feel more prepared to make choices that support both your health and your baby's well-being. Let’s dive in!
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When it comes to your blood pressure in pregnancy, being informed is key.
I’ve been excited for quite some time to write this blog not only because of how important this topic is, but also because of how many questions pregnant moms have surrounding it. This topic is relevant to every pregnant woman, and it’s my desire that you’ll be able to walk away from this blog feeling confident, clear, and engaged in your health — particularly your blood pressure.
Understanding your blood pressure patterns during pregnancy is crucial because it provides key insights into your overall health and helps identify potential complications. Changes in blood pressure may signal underlying issues such as pre-eclampsia, gestational hypertension, or other cardiovascular concerns—conditions that can impact both your well-being and your baby's.
The danger of elevated blood pressure isn’t just in the numbers themselves, but also in the cascade of interventions they can trigger, including unnecessary inductions that often lead to avoidable cesareans.
We'll begin by building a strong foundation, starting with a clear understanding of what blood pressure actually is, then continue the conversation talking about what affects it, signs and symptoms of hyper or hypotension, and why knowing your baseline is so crucial. By the end, you'll feel more empowered to keep an eye on your blood pressure and advocate for yourself during your pregnancy.
Ready to jump in?! Let’s get started!
What is blood pressure, exactly? Here are the basics to know.
To understand the big picture of blood pressure, we need to define some terms and start with a clear definition of what blood pressure really is.
Blood pressure is made up of two values.
The first value (top number) is your Systolic blood pressure (SBP). It measures the pressure on your vessels when your heart is squeezing (contracting).
The second value (bottom number) is your Diastolic blood pressure (DBP). It measures the pressure on your vessels when your heart muscle is relaxing (not squeezing).
Because the pressure on your vessels is higher when the heart is squeezing, the top number (SBP) will always be higher than the lower (DBP).
When blood pressure is higher than what is considered “normal” (we’ll talk more about this later), this is called hypertension. When it is lower, it’s called hypotension.
Blood pressure is represented in ranges and is defined the same way by the American Heart Association (AHA) and American College of Obstetricians and Gynecologists (ACOG) as:
Hypotension: Systolic 90 mmHg or less and Diastolic 60 mmHg or less
Normal: Less than 120/80 mmHg
Elevated: Systolic between 120 and 129 mmHg and Diastolic less than 80 mmHg
Stage 1 hypertension: Systolic between 130 and 139 mmHg and/or Diastolic between 80 and 89 mmHg
Stage 2 hypertension: Systolic at least 140 mmHg and/or Diastolic at least 90 mmHg
Now that you understand the basics of blood pressure, it's important to know what can affect it. Several factors can influence your BP during pregnancy, and being familiar with your normal range helps you better track any changes. This way, you can start applying what you've learned and be more in tune with how these factors may affect you personally as we explore them further.
Photo by Mockup Graphics on Unsplash
What can affect your blood pressure?
Blood pressure isn’t a “static” (or unchanging) measurement and can be affected by various factors. In pregnancy, your practitioner will often check to see if your blood pressure is within normal ranges or if you are showing signs of elevated blood pressure, or hypertension.
Since you’ll want to understand how your blood pressure is doing during pregnancy to make informed decisions, here are some of the factors to know that could be affecting your blood pressure during pregnancy:
Blood volume begins to increase early in pregnancy and continues to rise throughout. The American Heart Association concludes that the “total blood volume rises anywhere from 20% to 100% above pre-pregnancy levels but is usually closer to 45%.” Because of this volume increase, it’s not uncommon for blood pressure to increase, as well.
Stress, fear, and anxiety can also raise blood pressure. This happens when the body’s ‘fight-or-flight’ response gets triggered, causing the hormones adrenaline and cortisol to be released. These stress hormones can have several effects on the body, including but not limited to increasing blood pressure and heart rate.
Have you heard of “White Coat Syndrome”? This is characterized by someone having high blood pressure in a healthcare setting (such as a doctor’s office or hospital), or when they interact with a healthcare provider, but otherwise have a normal blood pressure in their normal environment. This can be somewhat common and is believed to be a result of anxiety. The ISSHP (International Society for the Study of Hypertension) suggests ‘white coat syndrome’ only be considered in pregnant women before 20 weeks of gestation. Hypertension present after that time is considered to be pregnancy-specific, otherwise known as gestational hypertension*,* but it's good to be aware that this phenomenon does exist*.*
Caffeine is considered a stimulant and therefore can increase your heart rate, blood pressure, and keep you awake. It’s important to mention that caffeine also crosses the placenta, affecting your baby in similar ways. If you do consume caffeine before a blood pressure reading, it’s best to wait at least 30 minutes before a measurement is taken.
Pain can make your blood pressure go up because of a response in your nervous system called the baroreceptor reflex. When you feel pain, your body tightens your blood vessels, which raises your blood pressure. Once the pain goes away, your blood pressure goes back to normal as your vessels relax.
A full bladder — it’s not uncommon for a mama to be told to come in for an ultrasound with a full bladder. This is because a full bladder can move the bowels aside, giving a clearer view of the uterus. But here’s the kicker — a full bladder can raise your systolic blood pressure a whopping 10 to 15 mmHg! So, if you’re asked to have a full bladder for an ultrasound, be sure to get the blood pressure reading after you’ve peed!
Faulty equipment or inaccurate readings by healthcare professionals happen. In fact, they happen often enough that my nursing school instructors taught us to check manually when a reading was abnormally high or low. If you know your baseline and your provider gets a funky reading, insist that your blood pressure be taken manually.
Recent activity like walking or running can increase your systolic blood pressure up to 20 mmHg. When demands are put on your muscles, your heart works harder and faster to circulate blood and supply them with oxygen. As a result, your blood pressure rises.
Photo by Bruno Nascimento on Unsplash
Behaviors and circumstances that increase blood pressure are only one side of the coin. There are also things that can decrease your blood pressure:
Nausea and vomiting in early pregnancy, commonly referred to as ‘morning sickness’, can cause a decrease in blood pressure by affecting blood volume. This is often seen as a result of dehydration.
Medication side effects (including but not limited to pain or anxiety medications)
Orthostatic hypotension (also called postural hypotension) happens when there is a sudden drop in blood pressure when quickly going to a standing position from a sitting or lying down position. Although more common in older adults, it is possible to see this in circumstances where a mama is on bed rest for long periods of time.
Loss of blood from bleeding, although less common, can lead to drops in blood pressure during pregnancy. An example would be vaginal bleeding from a subchorionic hemorrhage.
Long story short, knowing what can affect your blood pressure during pregnancy helps you stay on top of your health. By keeping an eye on these factors, you’ll be able to have better conversations with your practitioner and make smart decisions for you and your baby. Just remember, your blood pressure is only one part of the bigger picture, so stay informed and take things one step at a time to keep your pregnancy on track.
You’ll want to know your baseline blood pressure during pregnancy.
My blood pressure runs on the lower side. It’s not uncommon for my SBP to be less than 100 and my DBP to be in the 60s or 70s. In fact, I recently I went to my primary care provider, and the medical assistant couldn’t even get a reading. He seemed nervous, but I was cool, calm, and collected. Because I know myself -- I know my baseline. So, I was able to reassure him, and we moved on.
We mentioned in an earlier section that knowing your baseline is important for self-advocacy against unwanted interventions, but that’s not the only reason it’s a good idea to know yourself. Knowing your baseline blood pressure also provides a reference point for identifying changes and trends over time. Sudden or gradual and consistent changes from your baseline can indicate complications such as pre-eclampsia and are best treated when detected early.
So what’s the best way to get to know your blood pressure baseline? For starters, you’ll need access to a blood pressure machine. Revolutionary, right? If you want to have one for yourself, consider this model. I recommend getting an arm cuff vs a wrist cuff, as it’s typically a more accurate reading. Then, start recording!
Here are a few considerations to get you started:
Take it in the morning when you first wake up
Before and after a walk or anything counting as exercise
When you’re stressed and when you’re relaxed
Before and after a doctor’s appointment
After morning coffee
Before and after sex
During a headache
The scenarios in which you could take your blood pressure and it be different are endless. Some helpful tips would be to record which arm you used (I recommend consistently using the same arm as each arm can give very different readings), take blood pressure on bare skin or a thin piece of clothing (no blood pressure cuffs over hoodies or sweaters), and record the position you were in when you took it (laying down, sitting, or standing).
What to know if your blood pressure changes from your baseline in pregnancy?
Depending on your unique health profile moving into pregnancy, you may encounter variable blood pressure readings as you move through prenatal care. In the toggles below, we share more information on what may be happening when your blood pressure readings change from your baseline so you can be well informed of your options.
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Signs and symptoms of hypotension, or low blood pressure, can be hard to identify because they so often can be seen as just another side effect of pregnancy.
Some common symptoms include:
Nausea
Light headedness or dizziness
Weak feeling or tiredness
Fainting
Blurry eyesight
Confusion or lack of concentration
Clammy, pale, or cold skin
Most women feel some, if not all, of these things at some point or another during their pregnancy — so it can be hard to discern that her blood pressure is low.
Just like with hypotension, the signs of hypertension, or high blood pressure, can also be tricky to spot since they can resemble other common pregnancy symptoms. Be on the lookout for:
Edema (fancy word for ‘swelling’)
Headaches
Changes in vision (blurry or double vision)
Sudden weight gain
Nausea or vomiting
The best way to know if you’re experiencing high or low blood pressure is to take ownership of your health and track it for yourself. Then you'll have more baseline information to share and discuss with your practitioner.
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Sometimes hypertension is present before pregnancy. This is called Chronic Hypertension and is one of the most common types of hypertensions in pregnancy. Because hypertension has very few outward manifestations (especially if mild), it often goes undiagnosed. For this reason, women can be surprised with an elevated reading if they haven’t been checking their own blood pressure regularly prior to pregnancy.
However, there are other forms of pregnancy-induced hypertension to be aware of as you move through prenatal care. According to ACOG, the guidelines for diagnosing gestational hypertension should be as follows:
A mom 20 weeks’ gestation or later with a previous normal blood pressure reading
Two or more readings of SBP 140 or higher and/or a DBP of 90 or higher
Those two or more readings occurring at least 4 hours apart
These guidelines are important to know for self-advocacy. We have heard numerous (although even one is too many) testimonies of women planning for a natural birth only to be pressured into an induction after just ONE rogue blood pressure reading. These women often say that they check their blood pressure regularly at home and get normal readings, so the seemingly random one high reading seems out of place. These women often share how they’ve been able to remain calm and not rush to make big birth plan changes.
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Pre-eclampsia is a form of pregnancy-induced hypertension, but it is NOT diagnosed by high blood pressure alone
Pre-eclampsia is a condition that can show up in the second half of pregnancy (20 weeks or later) and is diagnosed by a sustained SBP of 160 mmHg or higher and at least one of the following:
Protein in the urine, indicating impaired kidney function
A low platelet count
Elevated liver enzymes, indicating impaired liver function
Fluid in the lungs leading to shortness of breath
New headaches that don’t go away after taking pain medication
New vision impairment
Pre-eclampsia can be a serious condition and requires close monitoring both by you and your provider.
We encourage you to be proactive about your blood pressure in pregnancy!
Okay! I know that was a lot of information, so we’ll wrap this up with this summary. Keeping tabs on your blood pressure is a big deal, especially when you're pregnant.
High or low blood pressure can impact you and your baby, so it's important to understand what influences those numbers and what to look out for.
Knowing your baseline blood pressure gives you a heads-up on any changes that might need attention. Regular self-checks or office checks mean you can catch potential issues early and get the right help if needed.
You're doing an amazing job taking proactive steps for a healthy pregnancy and birth. Thank you for allowing us to be part of the journey!
