High blood pressure (hypertension)
If you have high blood pressure, or hypertension, your heart has to work harder to pump the blood around your body. This can lead to weakening of the heart muscle.

Hypertension affects around 10-15% of pregnancies. There are three different types of hypertension in pregnancy:

• pre-eclampsia
• if you already have high blood pressure (chronic hypertension)
• high blood pressure as a result of pregnancy (gestational hypertension)

Pre-eclampsia
Pre-eclampsia affects 2-5% of pregnancies. It is usually diagnosed from around 20 weeks, and is most common in the third trimester of pregnancy. If untreated, it can lead to seizure (having a fit) and, on rare occasions, the mother’s death.

There are usually no symptoms to warn you that you have pre-eclampsia, and often the only way it can be detected is during the routine blood pressure and urine checks made by your doctor. Urine tests can reveal if there is protein in your urine, as this is often a sign of pre-eclampsia.

You will also be given a test to check whether your blood pressure is too high. Warning signs that pre-eclampsia may be progressing and medical advice is urgently needed are:

• swollen legs or ankles
• stomach pain
• severe headaches

It is vital to keep your antenatal appointments, or to reschedule them if necessary, as severe pre-eclampsia can affect both your health and your baby’s health. If left untreated, it can put you at risk from a stroke, impaired kidney and liver function, blood clotting problems, fluid on the lungs and seizures. Your baby may also be born prematurely or small or even stillborn.

There is no cure for pre-eclampsia, apart from delivering the baby and placenta, but it can be treated with drugs to lower blood pressure. You may have to go into hospital to be monitored, and your baby may need to be delivered early, depending on the severity of the condition.

While the root cause of pre-eclampsia is not known, studies suggest that the risk is higher if you are overweight when you become pregnant, so it’s a good idea to reach a healthy weight before trying for a baby. It is also more common if you have high blood pressure before becoming pregnant, or have had pre-eclampsia in a previous pregnancy. If this applies to you, attending regular check-ups to have your blood pressure and urine tested is even more important.

If you already have high blood pressure (chronic hypertension)
The second group affected by high blood pressure in pregnancy are women with chronic hypertension. In other words, women who already have high blood pressure before they become pregnant. This affects 1-3% of pregnancies. Some drug treatments for high blood pressure are not recommended in pregnancy. If you are taking tablets it is important to see your doctor to find out whether you need to change to other drugs before you become pregnant.

If you take drugs to lower your blood pressure, this can also reduce the blood flow to the placenta and your baby. It is important that your antenatal team monitors you closely to ensure that the growth of your baby remains normal.

While the type of treatment you are given will depend on the cause of your high blood pressure, the key to a healthy pregnancy is to ensure that your blood pressure remains under control. Again, having check-ups with your antenatal team is the best way to monitor your condition.

High blood pressure as a result of pregnancy (gestational hypertension)
The final group is by far the most common, affecting 5-10% of pregnancies. This is gestational hypertension, or high blood pressure caused by the extra stress pregnancy places on your body. This usually has no effect on you or your baby, and simply requires regular checks to ensure it doesn’t develop into anything more serious.

Many women with high blood pressure can hope for a natural vaginal delivery after 37 weeks. But if you have severe pre-eclampsia it may be necessary to deliver your baby early, possibly by caesarean section.

Find out more about what happens in labour, and your options for pain relief.