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Your blood pressure: Know the basics

For expectant mothers, every prenatal visit to a doctor, nurse, or midwife -- either in one-on-one or group prenatal care -- starts off pretty much the same way. Your vital signs are checked: body temperature, body weight (let's see how that baby is growing!), and blood pressure. This last measure is particularly important when you’re pregnant. And here’s why.

High blood pressure in pregnancy is an important diagnosis and indicator for preeclampsia, how the rest of your pregnancy is managed prior to delivery, the timing of delivery, risk of complications, and long-term maternal outcomes. However, according to the Council on Patient Safety in Women’s Health Care, “Blood pressure measurement is one of the most important basic clinical assessments that we do, yet it is often one of the most inaccurately performed assessments, leading to delays in diagnosis and treatment.”

As a patient, you can take charge of your health and overall well-being by understanding the basics of blood pressure, how it’s taken, and what you can do before, during, and after pregnancy. Because preeclampsia may be associated with increased risk of heart disease and stroke later in life, it’s more important than ever to monitor and manage your blood pressure throughout your lifetime.

High blood pressure is recorded as a ratio of two numbers: systolic blood pressure and diastolic blood pressure. Systolic blood pressure, which is the higher (or first) of the two numbers, measures the pressure in the arteries when the heart beats. Diastolic blood pressure, which is the lower (or second) of the two numbers, measures the pressure in the arteries between heartbeats or when the heart is resting.

To get an accurate reading, you should be positioned as follows when having your blood pressure measured. Here's an entertaining video on how to measure blood pressure:

  • Sitting or semi-reclining position with back supported and arm at heart level
  • No talking for at least five minutes before measurement
  • Bare upper arm without restrictive clothing
  • Feet should be flat, not dangling or crossed

 fig_pose_01_eng.png (122 KB)

Image credit: OMRAN

Other things that can affect the accuracy of your blood pressure reading include the presence of background noise, if you recently consumed any caffeine or nicotine, your weight, and using the wrong cuff size (whether it’s too small or too big).

Improper positioning alone can cause quite a dramatic increase in blood pressure. For example, if your back is unsupported, the diastolic blood pressure may be higher by 6 mmHg (Pickering TG et al; Circulation 2005). If your legs are crossed, systolic blood pressure may be higher by 2-8 mmHg (Pickering TG et al; Circulation 2005). If the arm is allowed to hang down unsupported, the blood pressure may be elevated by 10-12 mm Hg (O’Brien E; J Hypertension, 2003) and if the patient is talking, blood pressure may increase by 8-15 mm Hg.

There are important things you can do before, during, and after your pregnancy when it comes to blood pressure measurement:

  • Understand what normal blood pressure is – typically that’s anything less than 120 mm Hg systolic blood pressure and less than 80 mm Hg diastolic blood pressure.
  • Know your own normal blood pressure – this may vary and is important for ongoing monitoring both before and after pregnancy.
  • Reposition yourself for a more accurate reading, even if you aren’t asked to, and don't lie on your side to obtain a lower blood pressure, even if you're asked to.
  • Make sure providers are consistent and that they measure your blood pressure in the same arm, using the same position, and the same cuff size.
  • If your blood pressure reading is greater than 140/90 mm Hg, make sure they retake the measurement; if they don’t retake it on their own, do not hesitate to ask for a second (or third) reading.
  • Speak up if something seems off about your blood pressure reading.

Remember to be your own patient advocate if something doesn’t seem right – speak up and ask questions.

Photo used with permission from the Florida Perinatal Quality Collaborative and Jean Miles, MD

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