Understanding High Blood Pressure During Pregnancy

By Myrah M.

Blood pressure is the force of blood pumping and pushing against the walls of our arteries as the heart pumps blood. Blood pressure is read as two values – systolic pressure and diastolic pressure. A normal blood pressure is systolic pressure less than 120 and a diastolic pressure less than 80. High blood pressure is when the systolic pressure is 130 or higher, and the diastolic pressure is 80 or higher. Essentially, high blood pressure means that the pressure with which the blood is pumping in the body is too high for the body to sustain without getting damaged. Monitoring and controlling blood pressure during pregnancy is very important for the health and wellbeing of both baby and mother.

While it is normal for blood pressure to vary slightly during pregnancy, it is not safe for blood pressure to increase significantly enough to pose a risk to both a mother and her unborn baby. Pregnancy-induced hypertension (PIH), also known as gestational hypertension, occurs when there is an abnormal increase in blood pressure, typically after the 20th week of pregnancy.

Gestational hypertension is diagnosed when a pregnant woman has a blood pressure reading of 140/90 and higher without any preexisting high blood pressure. It occurs in about 3 in 50 women and is different from chronic hypertension, which is hypertension that already existed prior to pregnancy. It often occurs during the second half of the pregnancy and sometimes earlier in women pregnant with twins.

While PIH can occur in any pregnancy, it is more common in first pregnancies, twin pregnancies, overweight women, women with family history of PIH, women over the age of 35, women with diabetes, women with kidney disease, women with chronic hypertension, and women with prior PIH.

Types of Hypertension in Pregnancy

Hypertension occurs in about 10% of pregnancies, and the effect of the increased pressure on the body depends on the severity of the disease. There are three broad types of hypertension that can occur in pregnancy:

  • Chronic hypertension – women who had high blood pressure (over 140/90) prior to getting pregnant. While chronic hypertension might not be pregnancy-induced, it is a risk factor for gestational hypertension. Chronic hypertension can also worsen during pregnancy and can lead to preeclampsia.
  • Gestational hypertension – high blood pressure that manifests during pregnancy and resolves after delivery. Gestational hypertension can range from mild to severe. Gestational hypertension is truly pregnancy-induced and usually goes away about 12 weeks after childbirth. Sometimes, gestational hypertension is a result of chronic hypertension. Gestational hypertension can progress to preeclampsia, a more serious type of high blood pressure.
  • Preeclampsia – this is a very serious and potentially fatal disease that can result from both chronic and gestational hypertension. Preeclampsia can produce high levels of protein in the urine, which would be indicative of kidney damage. It can also cause other organ damage and could even lead to the death of mother and child if not treated immediately. Preeclampsia generally manifests in the later part of the pregnancy and is characterized by general swelling in the pregnant woman.
  • Eclampsia – this is a severe and dangerous form of preeclampsia that result in seizures as well as HELLP syndrome. HELLP syndrome is a life-threatening group of physical changes including red blood cell breakdown, changes in liver, and low platelets (so reduced ability to clot). HELLP stands for hemolysis, elevated liver enzymes, and low platelets. It usually develops around the 37th week of pregnancy and is usually foreshadowed by preeclampsia. Treatment requires prompt delivery of the baby.

Signs of High Blood Pressure in Pregnancy

High blood pressure during pregnancy typically causes headaches and blurred/double vision. More serious signs and symptoms that would require contacting your doctor immediately include:

  • Increased blood pressure
  • Fluid retention/swelling of your face or hands (edema)
  • Rapid weight gain
  • Decreased amount of urination
  • Changes in liver and kidney function tests
  • Pain around stomach especially in the upper right side of belly
  • Nausea or vomiting
  • Severe headaches that do not respond to medication

Hypertension in pregnancy has detrimental effects on a fetus. Depending on the severity of the high blood pressure, pregnancy complications from hypertension can include low birth weight, premature delivery, placental separation, and other health problems for the unborn child.

Causes of Pregnancy-Induced Hypertension

The exact cause of pregnancy-induced hypertension is unknown, but some factors that increase the risk of developing high blood pressure (or worsened high blood pressure) during pregnancy include:

  • High blood pressure before pregnancy (pre-gestational hypertension)
  • Obesity
  • Kidney disease
  • Diabetes
  • Being pregnant with multiples – twins, triplets
  • Severe stress
  • Age – younger than 20 and older than 40 years
  • Race – African American ancestry
  • Family history of gestational hypertension
  • Gestational hypertension in previous pregnancies

Diagnosis of Gestational Hypertension

Gestational hypertension can be diagnosed through blood pressure readings, blood clotting tests, kidney and liver function tests, monitoring weight, checking for fluid retention and swelling, and testing the urine for signs of protein (kidney damage).

Treatment of Gestational Hypertension

The goal of treating gestational hypertension is to prevent it from worsening and causing more harm to mother and baby. Treatment options include:

  • Antihypertensive medications
  • Bedrest either at home or at the hospital
  • Lab testing of blood and urine
  • Steroids to help the premature baby’s lungs mature in case of early delivery
  • Fetal monitoring through:
    • Measuring fetal heart rate in response to the fetus movement
    • Keeping track of fetal movement to monitor fetal distress
    • Ultrasounds to observe fetus
    • Doppler flow studies to measure the flow of blood through the blood vessels
    • Monitoring your baby using an at-home doppler monitor

How to Prevent Pregnancy-Induced Hypertension

Unfortunately, there is no sure way to prevent PIH. However, keeping your blood pressure at 120/80mmHg or lower can help reduce the risk of developing complications from hypertension.

Other things you can do to reduce the risk of developing or exacerbating an existing hypertension include:

Keep your doctor’s appointments. Early detection is key to a better outcome with hypertension in pregnancy. By keeping your routine appointment with your doctor, you and your physician can monitor your blood pressure closely for the duration of your pregnancy.

Eat a healthy diet. This includes eating plenty of vegetables and fruits, whole grains, lean protein sources like chicken and fish, low-fat dairy products, and healthy fats like olive oil and nuts.

Limit salt intake. Sodium causes water retention, which increases blood pressure levels. It's best to limit sodium intake to less than 2,000 milligrams per day (about one teaspoon of salt). If possible, avoid processed foods that contain high amounts of sodium additives.

Exercise regularly, but not too vigorously. Prioritizing exercise can help lower your blood pressure and improve your overall health during pregnancy. Always check with your doctor before starting a new exercise regimen, especially if you have pre-existing conditions that might make exercise risky for you or your baby.

Monitor your weight. Gaining too much weight during pregnancy can put extra strain on your heart and blood vessels and this can raise your blood pressure levels. Keep an eye on your weight so that you gain just the recommended healthy amount. Your doctor will record your weight every visit and can advise you on how to manage your weight depending on your starting weight, how many babies you’re having, and other factors.

Get more rest and sleep. Sleep deprivation can raise blood pressure levels in pregnant women, event those with no existing high blood pressure. Developing good sleeping habits early on in your pregnancy may help reduce stress and lower your risk for complications during delivery time.

Take medications as prescribed. If you take antihypertensives before pregnancy, continue taking them as directed by your doctor. This will you help a maintain healthy blood pressure throughout your pregnancy.

Drink lots of water. Dehydration can cause an increase in blood pressure, so staying well-hydrated is crucial, especially if you’re already taking certain blood pressure medications that increase urination such as diuretics.

The Real Danger of Pregnancy-Induced Hypertension

While PIH is relatively rare, it’s still a potentially dangerous condition for both mother and child.

During pregnancy, the placenta provides the developing baby with nutrients and oxygen. When the mother’s blood pressure is higher than normal, the increase in blood pressure can damage the placenta. If the placenta does not get enough blood flow, the fetus will in turn get less oxygen and nutrients, leading to congenital disabilities and other pregnancy complications. When high blood pressure worsens and leads to preeclampsia and eclampsia, serious problems can occur, including stillbirth, seizures, low birth weight, (premature) placental abruption/detachment, and even death of the mother and child.

How to Monitor Blood Pressure During Pregnancy

The American Heart Association also recommends that all pregnant women measure their blood pressure regularly between weeks 16 and 28 of pregnancy (around 26 weeks). This is because most cases of preeclampsia happen around this time. If you have a history of high blood pressure prior to pregnancy or a family history of PIH, your doctor may recommend starting self-monitoring at home from the onset of your pregnancy rather than waiting until 16 weeks. This can help you detect potential problems early and get the treatment you need. You will need a home blood pressure device to self-monitor your pressure at home. These are available at most pharmacies or online. You can buy one specifically designed for pregnant women or use an adult cuff with a larger opening around the arm if needed. You can also use a fetal doppler to monitor your baby's heartbeat for your peace of mind.

Pregnancy-induced hypertension can be a serious problem, but it is also preventable. By understanding your blood pressure and working to keep it under control, you can ensure a safe and healthy pregnancy.

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