What is blood pressure?
Blood pressure is vital to the working of the body's circulatory system, which is made up of the heart, the arteries and the veins. In part, blood pressure is created by the steady beat of the heart. Each time the heart relaxes or contracts, it pumps blood into the arteries. The arteries carry blood to the organs of the body, while the veins return blood to the heart.
The small arteries, called arterioles, also affect blood pressure. These blood vessels are covered by a layer of muscle. When blood pressure is normal, that layer of muscle stays relaxed and the arterioles are dilated (open), so that blood flows through them easily. If a signal is sent to raise the blood pressure, however, the muscle layer tightens and the arterioles narrow, so that blood flows less easily and the pressure in the arteries therefore rises. This is called high blood pressure, or hypertension.
How can high blood pressure affect pregnancy?
When a woman has high blood pressure during pregnancy, the blood flow to the placenta may be reduced. As a result the fetus receives less oxygen and fewer nutrients than it needs, which can slow its growth.
What is chronic hypertension?
When high blood pressure has been present for some time before a pregnancy, it is known as chronic hypertension, or simply hypertension. This condition continues during the pregnancy and after the baby is born. It is important that chronic hypertension is controlled, because it can lead to health problems such as a heart attack or a stroke.
How can chronic hypertension be controlled in pregnancy?
During pregnancy, chronic hypertension can also affect the growth of the fetus. If you are taking medication to control your blood pressure, your doctor will decide whether it is safe to continue taking it in pregnancy. Many women with chronic hypertension can stop their medication during pregnancy because their blood pressure becomes normal. Other women need to continue their medication. In some cases a woman may need to change medication, so that her blood pressure stays within normal limits while her pregnancy remains safe.
I have chronic hypertension. Are there steps I can take before pregnancy so that a future pregnancy is safer?
The following steps can help you have a safer pregnancy:
- Lose weight through a healthy diet and exercise.
- Take your blood pressure medication exactly as prescribed.
- Ask your doctor whether your medication is safe during pregnancy.
What is gestational hypertension?
When high blood pressure is first noticed in the second half of pregnancy, it is called gestational hypertension. This type of high blood pressure disappears soon after the baby is born. You may need to see your doctor more often so that your blood pressure can be checked. When gestational hypertension occurs together with other findings, the condition is called preeclampsia.
What is preeclampsia?
Preeclampsia is a serious medical condition that affects every organ of the body. It puts stress on the kidneys, for example, so that increased amounts of protein appear in the woman's urine. Other signs of preeclampsia may include:
- Headaches
- Vision problems
- Rapid weight gain
- Swelling (oedema) of the hands and face
What causes preeclampsia?
It is not known why some women develop preeclampsia. Some women are at higher risk than others, however. The risk of developing preeclampsia is increased in women who:
- Are pregnant with their first child
- Had preeclampsia in a previous pregnancy
- Have a history of chronic hypertension
- Are 35 years old or older
- Are carrying more than one baby
- Have certain medical conditions, such as diabetes or kidney disease
- Are obese
- Are of African-American descent
- Have autoimmune diseases, such as lupus, or blood disorders
What happens if a woman has preeclampsia?
A woman with preeclampsia may need to be admitted to hospital so that she and her baby can be monitored. In some cases the baby may be born preterm. When preeclampsia is severe, the woman's organs can be damaged, including the kidneys, liver, brain, heart and eyes. In other cases seizures may occur; this is called eclampsia.
How is preeclampsia treated?
If preeclampsia develops, the only real treatment is delivery. The decision to deliver the baby depends on the risks to both the woman and the baby. Birth may happen naturally or labor may be induced. Sometimes a cesarean section is needed, depending on the condition of the woman and the baby. Before deciding on an early delivery, your obstetrician may wait to see whether your condition improves. During labor you may be given medication to prevent seizures or to lower your blood pressure.
Glossary
Cesarean delivery: the birth of a baby and delivery of the placenta through an incision made in a woman's abdomen and uterus.
Eclampsia: seizures occurring in pregnancy and linked to high blood pressure.
Placenta: tissue that provides nourishment to and takes waste away from the fetus.
Preeclampsia: a condition of pregnancy in which there is high blood pressure and protein is found in the urine.