What is hypertension and when should I worry?
As a maternal–fetal medicine doctor, I often discuss blood pressure with pregnant patients. While it is one of the most important vital signs we watch, it can also be confusing and anxiety provoking for patients.
In this blog, we will discuss:
- What exactly is “high blood pressure” or “hypertension”?
- Why does hypertension matter so much in pregnancy?
- How do I know when to call my doctor—or go straight to Labor & Delivery?
For non-pregnant people, blood pressure guidelines can be a bit flexible. In pregnancy, we have a hard line.
Pre-existing (also called Chronic) Hypertension is defined as a blood pressure reading of 130/80 mm Hg or higher before 20 weeks and outside of pregnancy.
It does not matter if only the top number (systolic) is high, or only the bottom number (diastolic) is high. If either number crosses that threshold on two occasions at least 4 hours apart, we diagnose you with hypertension. However, not all high blood pressure is the same.
In Maternal-Fetal Medicine, we categorize pregnancy hypertension into three main buckets:
1. Chronic Hypertension
This means you had high blood pressure before you got pregnant, or you were diagnosed with it before 20 weeks of gestation. If you are in this category, our goal is to manage your medication to keep your pressure stable while the baby grows.
2. Gestational Hypertension
This is high blood pressure that develops at 20 weeks of pregnancy or later. The key here is that while your pressure is high, your other organs (kidneys, liver) are functioning normally, and you do not have protein in your urine.
3. Preeclampsia
This is the condition we work hardest to prevent. Preeclampsia occurs when you have high blood pressure in addition to signs that other organ systems are struggling. This usually involves protein in the urine (kidney stress), low platelets, elevated liver enzymes, or other findings. Preeclampsia can progress rapidly and is dangerous for both mother and baby.
Safety Risk For Mother & Baby
High blood pressure causes the blood vessels to constrict (tighten).
- For the Baby: Constricted vessels mean less blood flow to the placenta and poor placental development. This can lead to fetal growth restriction (the baby measuring small) or low amniotic fluid.
- For the Mom: Uncontrolled hypertension puts you at risk for stroke, seizure (Eclampsia), and organ damage.
Why does hypertension matter in pregnancy?
Uncontrolled high blood pressure—especially preeclampsia—can increase the risk of:
For you:
- Stroke or very high blood pressure emergencies
- Seizures (eclampsia)
- Organ injury (kidneys, liver, brain)
- HELLP syndrome (a severe variant with hemolysis, elevated liver enzymes, low platelets)
- Placental abruption (early separation of the placenta)
- Complications during or after delivery
For your baby:
- Poor growth (fetal growth restriction)
- Low amniotic fluid
- Preterm birth (sometimes medically recommended to protect you or the baby)
- Stillbirth in severe, untreated cases
However, with close monitoring and timely treatment, most people with hypertension during pregnancy do well and have healthy babies. Recognizing signs early is key.
When to call your doctor
If you experience any of the following, do not wait for your next appointment. Call your OB or go to Triage/Labor & Delivery immediately:
- The Unrelenting Headache: This is a severe headache (often in the front or back of the head) that does not go away with Tylenol, water, or rest.
- Visual Changes: Seeing “spots” or floaters, flashing lights, or sudden blurriness.
- Upper Right Quadrant Pain: Severe pain just below your ribs on the right side. Many patients mistake this for bad heartburn or the baby kicking the ribs, but it can actually be liver pain.
- Sudden, Severe Swelling: Some swelling is normal in pregnancy. However, if your face becomes puffy, or your hands swell so much that your rings won’t come off suddenly.
- Shortness of Breath: Difficulty breathing when lying flat.
- Severe Hypertension: systolic BP (the top number) of 160 or higher, or diastolic (the bottom number) BP 110 or higher
While hypertension can impact a pregnancy journey, it can also be managed. A patient will likely have more ultrasounds and fetal monitoring, and perhaps an earlier delivery date, to help increase the chances of a healthy delivery.