Preventing high blood pressure during pregnancy starts before or early in pregnancy, with a combination of physical activity, healthy weight gain, and in some cases, low-dose aspirin. Not every case is preventable, but several evidence-backed strategies can meaningfully lower your risk of developing gestational hypertension or preeclampsia.
Blood pressure during pregnancy is considered high when it reaches 140/90 mm Hg or above. When this develops after the 20-week mark in someone who previously had normal readings, it’s called gestational hypertension. Preeclampsia is a more serious form that involves organ damage, typically affecting the kidneys or liver.
Know Your Risk Level First
Your prevention plan depends heavily on where you fall on the risk spectrum. High-risk factors include a history of preeclampsia in a previous pregnancy, carrying twins or multiples, having chronic high blood pressure or diabetes (type 1 or type 2) before pregnancy, kidney disease, or autoimmune conditions like lupus. A single one of these factors puts you in the high-risk category.
Moderate-risk factors are more common: being a first-time mother, having a BMI over 30, a family history of preeclampsia (particularly a mother or sister), being 35 or older, conceiving through IVF, having a gap of more than 10 years since your last pregnancy, or having a lower income. Black women also face a higher risk, which researchers attribute largely to the cumulative effects of systemic racism and disparities in healthcare access. Having two or more moderate-risk factors moves you into a category where preventive medication is recommended.
Low-Dose Aspirin for High-Risk Pregnancies
The single most studied preventive intervention is daily low-dose aspirin, 81 mg per day. Both the U.S. Preventive Services Task Force and the American College of Obstetricians and Gynecologists recommend it for anyone with one high-risk factor or multiple moderate-risk factors. It should be started between 12 and 28 weeks of gestation, ideally before 16 weeks, and continued daily until delivery.
The evidence behind this recommendation is strong. The USPSTF found with moderate certainty that daily low-dose aspirin substantially reduces the risk of preeclampsia, preterm birth, and perinatal mortality in high-risk pregnancies. This isn’t something to start on your own; your prenatal care provider will assess your risk factors and prescribe it if appropriate. But if you know you have risk factors, it’s worth raising the topic early in pregnancy so you don’t miss the optimal window.
Exercise Starting Early in Pregnancy
Regular physical activity is one of the most effective lifestyle strategies. The Community Preventive Services Task Force specifically recommends exercise programs that begin before the 16th week of pregnancy and continue through delivery. Two formats have the best evidence behind them:
- Supervised exercise classes at least three times per week, with 30 to 60 minutes of moderate-intensity aerobic activity per session
- Regular walking totaling 90 to 150 minutes per week, or roughly 11,000 steps per day
Moderate intensity means you can carry on a conversation but feel noticeably warmer and more winded than at rest. Swimming, stationary cycling, prenatal yoga with an aerobic component, and brisk walking all count. The key detail is consistency and starting early. Exercise programs that begin after the second trimester don’t show the same protective effect.
Weight Gain Within Recommended Ranges
Gaining too much weight during pregnancy increases blood pressure risk, but gaining too little creates its own problems. The targets depend on your pre-pregnancy BMI:
- Underweight (BMI under 18.5): 28 to 40 pounds
- Normal weight (BMI 18.5 to 24.9): 25 to 35 pounds
- Overweight (BMI 25 to 29.9): 15 to 25 pounds
- Obese (BMI 30 to 39.9): 11 to 20 pounds
For twin pregnancies, the ranges are higher. A normal-weight person carrying twins should aim for 37 to 54 pounds, while someone with a BMI over 30 should aim for 25 to 42 pounds. These ranges come from the Institute of Medicine and are the standard used by the CDC. Steady, gradual gain is more important than hitting an exact number. Rapid weight gain in the second or third trimester can itself be an early sign of preeclampsia due to fluid retention, so tracking your weight gives you useful information beyond just nutrition.
What to Eat (and What Doesn’t Help)
You may have heard that the DASH diet, which is effective for lowering blood pressure outside of pregnancy, works the same way for pregnant women. The reality is more nuanced. A study published in the Journal of the American Heart Association found that higher adherence to the DASH diet was associated with modestly lower diastolic blood pressure in mid-pregnancy, but it did not reduce the actual risk of developing gestational hypertension or preeclampsia in low-risk women. Larger observational studies in American and Danish populations found no significant association either.
That said, a diet rich in fruits, vegetables, whole grains, and lean protein while limiting processed meat, added sugars, and excess fat is still a sound foundation. The specific nutrient with the clearest preventive evidence is calcium. The World Health Organization recommends 1.5 to 2 grams of supplemental calcium daily for pregnant women whose diets are low in calcium, specifically to reduce preeclampsia risk. If you regularly consume dairy, fortified foods, or other calcium-rich sources, you may already be meeting your needs. If not, supplementation is worth discussing with your provider.
Sodium is an interesting case. Restricting salt has not been shown to prevent preeclampsia when studied in isolation, and blanket salt restriction is not currently recommended during pregnancy. However, one analysis found that women consuming about 3.7 grams of sodium per day had a 20% greater risk of preeclampsia compared to those consuming about 2.6 grams. For context, the average American diet contains well over 3 grams of sodium daily. So while aggressive salt restriction isn’t the answer, keeping sodium at a moderate level by limiting processed and packaged foods is reasonable. Vitamins C and E, magnesium, fish oil, and zinc supplements have all been studied and shown no effect on preeclampsia risk.
Monitoring Your Blood Pressure at Home
Home blood pressure monitoring can help you catch rising numbers between prenatal visits. If you decide to track at home, the device matters: standard consumer cuffs are not all validated for use during pregnancy, because the cardiovascular changes of pregnancy can affect accuracy. The British and Irish Hypertension Society and STRIDE BP maintain lists of monitors that have been independently tested and approved for pregnant women. An upper-arm cuff is preferred over a wrist model.
That said, current evidence from NHS England’s review notes that no large trial has demonstrated that home self-monitoring changes clinical outcomes in pregnancy. The value is primarily in catching a trend early, particularly if you have risk factors or live far from your care provider. It’s a supplement to, not a replacement for, the blood pressure checks at your prenatal appointments. If you see readings consistently at or above 140/90, contact your provider rather than waiting for your next scheduled visit.
What You Can Do Before Pregnancy
If you’re planning a pregnancy and have modifiable risk factors, the preconception window is your best opportunity. Reaching a healthier BMI before conceiving reduces your baseline risk. Getting blood pressure, blood sugar, and kidney function checked establishes whether you have chronic conditions that would place you in the high-risk category from day one. If you already take blood pressure medication, you’ll need to discuss which medications are safe to continue during pregnancy, since some commonly used drugs are not recommended.
Building an exercise habit before pregnancy also matters, because the evidence for exercise in preventing gestational hypertension is strongest when activity begins in the first trimester. Starting from a baseline of regular movement makes that transition much easier than trying to build a new routine while dealing with first-trimester fatigue.