High blood pressure during pregnancy is relatively common, affecting an estimated 6 to 8 percent of pregnancies in the United States. Globally, preeclampsia alone occurs in 3 to 8 percent of pregnancies, and hypertensive disorders collectively are responsible for roughly 16 percent of maternal deaths worldwide. While many cases are mild and manageable, pregnancy-related hypertension is one of the leading causes of serious complications for both mother and baby.
Types of High Blood Pressure in Pregnancy
Not all pregnancy hypertension is the same. There are four distinct types, and the differences matter because they carry different levels of risk and require different management.
Gestational hypertension is elevated blood pressure that develops after 20 weeks of pregnancy in someone whose blood pressure was previously normal. The reading reaches 140/90 mm Hg or higher, but there’s no sign of organ damage. In many cases, blood pressure returns to normal after delivery.
Preeclampsia also develops after 20 weeks in a previously healthy pregnancy, but it involves more than just high blood pressure. It can affect the kidneys, liver, and blood’s ability to clot. This is the form that carries the most acute danger during pregnancy.
Chronic hypertension means you had high blood pressure before getting pregnant, or it was detected before the 20-week mark. This type doesn’t go away after delivery because it existed independently of the pregnancy.
Chronic hypertension with superimposed preeclampsia is when someone with pre-existing high blood pressure then develops signs of preeclampsia on top of it. This combination increases risk significantly.
How It’s Diagnosed
During pregnancy, hypertension is diagnosed when blood pressure reaches at least 140 mm Hg systolic (the top number) or at least 90 mm Hg diastolic (the bottom number) on two separate readings taken at least four hours apart. This is why prenatal visits include a blood pressure check every time.
Blood pressure at or above 160/110 mm Hg is classified as severe and needs to be confirmed within minutes so treatment can start quickly. At this level, the risk of stroke and organ damage rises sharply.
Who Is at Higher Risk
Certain factors make pregnancy hypertension more likely. A first pregnancy carries higher risk than subsequent ones. Being over 35, having a BMI in the obese range, or carrying multiples (twins or more) all increase the odds. A personal or family history of preeclampsia is one of the strongest predictors. Pre-existing conditions like diabetes, kidney disease, or autoimmune disorders also raise risk, as does having had high blood pressure in a previous pregnancy.
Race plays a role as well. Black women in the United States experience preeclampsia at significantly higher rates than white women, a disparity driven by a combination of systemic health inequities, chronic stress, and differences in access to prenatal care.
What It Means for Mother and Baby
When blood pressure stays mildly elevated and is monitored closely, many pregnancies proceed without serious problems. But when hypertension is severe or progresses to preeclampsia, the stakes rise quickly.
For the mother, chronic hypertension during pregnancy is linked to roughly 2.6 times the risk of stroke or acute heart events and 3.5 times the risk of postpartum death compared to pregnancies without hypertension, based on large-scale French data from 2010 to 2018. Preeclampsia can damage the kidneys and liver, reduce the blood’s clotting ability, and in rare cases progress to seizures (a condition called eclampsia).
For the baby, the risks are equally serious. Chronic hypertension roughly doubles the likelihood of preterm birth and increases the chance of the baby being born smaller than expected. Infant death is also more likely, with about 1.8 times the risk compared to pregnancies without hypertension. These outcomes occur because high blood pressure can reduce blood flow through the placenta, limiting the oxygen and nutrients reaching the baby.
Warning Signs to Watch For
Preeclampsia sometimes develops without obvious symptoms, which is one reason regular prenatal visits are so important. But when symptoms do appear, they tend to come on suddenly and can escalate fast. The key warning signs include:
- Severe headaches that don’t respond to typical pain relief
- Vision changes such as blurred vision, light sensitivity, or temporary vision loss
- Upper belly pain, usually under the ribs on the right side
- Sudden swelling of the face and hands
- Shortness of breath caused by fluid buildup in the lungs
- Nausea or vomiting in the second half of pregnancy
- Sudden weight gain over a few days
Any of these warrants an immediate call to your provider or a trip to the emergency room. Mental confusion or altered behavior can signal that seizures are imminent.
Prevention With Low-Dose Aspirin
For people identified as high risk, daily low-dose aspirin (81 mg) can reduce the chances of developing preeclampsia. ACOG recommends starting it between 12 and 28 weeks of pregnancy, ideally before 16 weeks, and continuing daily until delivery. This isn’t recommended for all pregnancies, only for those with specific risk factors like a history of preeclampsia, chronic hypertension, or carrying multiples. Your provider will assess your individual risk profile to determine whether aspirin is appropriate.
What Happens After Delivery
For gestational hypertension and preeclampsia, delivery is the definitive treatment. Blood pressure usually begins to normalize in the days and weeks following birth. But “after delivery” doesn’t mean the danger is immediately over. Preeclampsia can develop or worsen postpartum, sometimes in women who had no signs of it during pregnancy.
ACOG recommends that women who had hypertensive disorders during pregnancy have their blood pressure checked no later than 7 to 10 days after delivery. Those with severe hypertension should be seen within 72 hours, and some experts recommend a check at 3 to 5 days. Postpartum preeclampsia carries the same risks as the prenatal form, so persistent headaches, vision changes, or severe swelling after delivery shouldn’t be dismissed as normal recovery discomfort.
There’s also a longer-term picture to consider. Having preeclampsia or gestational hypertension increases the risk of cardiovascular disease later in life. Women with a history of pregnancy hypertension benefit from ongoing blood pressure monitoring and heart health screening in the years that follow.