High Blood Pressure

What is hypertension and how is it measured?

If you have “hypertension”, it means your blood pressure is high. Blood pressure is measured by a cuff placed on your upper arm, and the measurements include systolic and diastolic values. The diastolic pressure is the “bottom number” of the blood pressure reading and reflects the pressure in your arteries when the heart is at rest and filling. If the diastolic blood pressure is consistently higher than 90 mm Hg, it means that you likely have hypertension. The systolic value is the “top number” and reflects the amount of pressure your heart has to generate to pump blood to the rest of your body. If it’s greater than 140 mm Hg, that is also abnormal. If both values are high, it usually means that blood pressure is high. Sometimes the systolic value is temporarily high because of stress, anxiety or pain, and therefore is a less reliable way of diagnosing blood pressure. That’s why, in pregnancy, we focus more on the diastolic value: Hypertension is diagnosed if the diastolic is higher than 90 mm Hg on several readings.

How should hypertension be treated BEFORE pregnancy?

Some women have hypertension even before becoming pregnant, which is known as chronic hypertension. The cause of chronic hypertension is most commonly due to genetics (runs in your family), increased age, related to lifestyle (for instance a diet that is high in salt and fat, being overweight, smoking), or for no reason that can be identified. Sometimes, women also have a medical condition such as diabetes, kidney disease or heart disease, which makes lowering blood pressure especially important in order to prevent long-term complications like heart attack or stroke.

Before becoming pregnant: If you have chronic hypertension before becoming pregnant, changes in diet, weight loss, and increasing physical activity can be helpful ways of controlling blood pressure control. Please check with your doctor/specialist first to make sure it’s safe for you to start exercising, especially if you have heart disease.

If you’re already on blood pressure medication, you should review the safety of your drug(s) with your doctor. Some medications are considered safe in pregnancy and include: labetalol, methyldopa, nifedipine, and hydralazine. Other drugs are not safe in pregnancy including the class of drugs known as “ACE-inhibitors” and “angiotensin-receptor blockers” (also known as ARB’s). These drugs may need to be switched to a safer medication before you become pregnant and you should discuss this with your specialist first. Do not stop medications without first checking with your doctor! The MOTHERISK website is an excellent resource.

Blood pressure control before pregnancy is very important. Women who have chronic hypertension can go through pregnancy safely, but may need a referral to a specialist for management.

How should hypertension be treated DURING pregnancy?

Interestingly, blood pressure often improves in the first half of pregnancy. Therefore if you have hypertension before pregnancy, the dose of your medication may actually need to be decreased. However, blood pressure often rises in the third trimester and women who have chronic hypertension before pregnancy are at an increased risk of developing preeclampsia (see below). We do not yet know what the optimal blood pressure in pregnancy is, but do know that we should avoid the extremes of blood pressure so that it’s not too high or too low. The target blood pressure in pregnancy is pretty broad (anywhere from 80-105 mm Hg diastolic), and will depend on whether you have other medical conditions. You should have your blood pressure checked regularly in pregnancy.

If you have severe hypertension in pregnancy, usually defined as a systolic pressure greater than 160 mm Hg, your baby is at risk of growth restriction (being small). There is also a small risk of placental abruption (the placenta separates prematurely from the uterus). Also, if you develop preeclampsia (see below), you have to deliver prematurely. Your doctor may monitor the baby’s growth more closely. Treating severe hypertension can be helpful in preventing these problems.

What is Preeclampsia?

Some women develop high blood pressure only in pregnancy, and that’s known as “Gestational Hypertension”. Some of these women will also develop preeclampsia (previously known as “toxemia”).

Gestational Hypertension
This group of women develops high blood pressure because of the pregnancy. This type of hypertension can start anytime after 20 weeks gestation, is most commonly mild occurring close to the end of pregnancy, and resolves after pregnancy. You may or may not need medication to treat it.

Preeclampsia
This type of hypertension also only occurs in pregnancy, starting anytime after 20 weeks gestation (but usually towards the end of pregnancy), and is a much more serious medical condition. The cause of preeclampsia is unknown, but it’s thought to be somehow related to the placenta. Some risk factors include: first pregnancy, a history of preeclampsia in your mother or sister, if you’ve had preeclampsia in a previous pregnancy, and certain medical conditions like chronic hypertension, diabetes, and kidney failure. Preeclampsia is a process that can make blood pressure go very high, can cause swelling to develop very quickly, and can affect multiple organs including the liver, the kidneys, the lungs, and the blood system. In rare cases, it can lead to seizure or stroke.

We can diagnose preeclampsia when blood pressure starts to rise, and if there is protein in the urine on dipstick. You should seek medical attention if you start having severe headaches, swelling that develops very quickly (especially in your hands and feet), pain in your upper abdomen, or notice that the baby isn’t moving as much as before.

The treatment includes close monitoring of both you and your baby (often in hospital), keeping your blood pressure under control, and checking your lab tests frequently. However, the process can only really be stopped by delivery, often before the due date. Delivering prematurely is a serious decision, but may be necessary if either you or the baby is not well.

How is hypertension treated after pregnancy?

If you had chronic hypertension, this will likely continue after the delivery. Medications that are considered safe in breastfeeding include labetalol, methyldopa, nifedipine, hydralazine.

If you’ve developed preeclampsia, you may have had to stay in hospital longer than expected before everything improves. You may still be on blood pressure medication when you are discharged home. After being discharged you should see a doctor regularly to check your blood pressure. Hypertension from preeclampsia may take weeks (in some cases months) to resolve completely.

Research has shown that women who develop gestational hypertension or preeclampsia have a 30% risk of developing chronic hypertension in the next 10 years. It is important that you see your family doctor yearly to check your blood pressure, and that you follow a healthy lifestyle to try to reduce that risk as much as you can.