A blood pressure reading is given as two numbers. The first number represents the pressure created when your heart beats (systolic pressure); the second number is the pressure when the heart is at rest between beats (diastolic pressure). Your blood pressure (measured in millimetres of mercury, or mm Hg for short) is recorded regularly during your pregnancy. It is recorded as a higher (systolic) pressure and a lower (diastolic) pressure – for example, 120/70 mm Hg, or 120 over 70.
High blood pressure is defined as a reading of 140/90 or higher, even if just one of the numbers is higher. If you have high blood pressure, or hypertension, your heart has to work harder to pump the blood around your body.
Most pregnant women with high blood pressure have healthy babies, but a few have problems. High blood pressure problems occur in 5 percent to 10 percent of all pregnancies in the Nigeria. Globally, by conservative estimates, hypertensive disorders are responsible for 76,000 maternal and 500,000 infant deaths every year thus remaining one of the leading causes of maternal and infant illness and death. The complications may be mild or severe, and can include preterm labor and low birth weight. High blood pressure during pregnancy can also cause less blood to flow through the placenta, delivering less oxygen and fewer nutrients to your growing baby.
There are four types of high blood pressure that can affect pregnant women:
Chronic hypertension: This is ongoing high blood pressure that’s diagnosed before pregnancy or before the 20th week of pregnancy. If a woman is diagnosed with gestational hypertension (starting after 20 weeks) and her blood pressure is still high 12 weeks after delivery, the condition is also considered chronic.
Many women with chronic hypertension will be taking drugs to keep their blood pressure within the range that is best for them (the target range). As blood pressure falls during the first half of pregnancy, it is sometimes possible to stop anti-hypertensive drugs, at least temporarily.
If you take drugs to lower your blood pressure, this can reduce the blood flow to the placenta and to your baby. It is important that your antenatal team monitors you closely to ensure that the growth of your baby remains normal.
Having chronic hypertension significantly increases your risk of developing preeclampsia. Preeclampsia that develops when you already have chronic hypertension is called “Superimposed Preeclampsia.” About 1 in 4 women with chronic hypertension and as many as half of women with severe chronic hypertension will develop superimposed preeclampsia during pregnancy. Chronic hypertension increases your risk for a number of pregnancy complications, including intrauterine growth restriction, preterm birth, placental abruption, and stillbirth.
Gestational hypertension: Sometimes referred to as Pregnancy-induced hypertension (PIH), this form of high blood pressure develops after 20 weeks of pregnancy and goes away after delivery. Pregnancy-induced hypertension, or gestational hypertension, affects around 16% of pregnancies. This means that out of 100 pregnant women, 16 will develop high blood pressure in pregnancy.
It depends on how far along you are in pregnancy when you develop gestational hypertension and how high your blood pressure gets. The more severe your hypertension and the earlier in pregnancy it appears, the greater your risk for problems.
The good news is that most women who get gestational hypertension have only a mild form of the condition and don’t develop it until near term (28 weeks or later). If you’re in this category, you still have a somewhat higher risk of being induced or having a c-section, but other than that, you and your baby are likely to do as well as you would if you had normal blood pressure.
Preeclampsia: This is a serious disorder that occurs when a pregnant woman has high blood pressure and protein in her urine after 20 weeks of pregnancy. Untreated preeclampsia can cause serious complications to mother and baby that could become fatal.
Preeclampsia affects 3 to 8 percent of pregnant women, and it’s even more common among women of African descent, if you have high blood pressure before becoming pregnant, or if you have had pre-eclampsia in a previous pregnancy.
Pre-eclampsia can run in families, and affects around 3-5% of pregnancies. Problems usually start towards the end of pregnancy, after around week 28, but can occur earlier. It can also happen after the birth. It is likely to be more severe if it starts earlier in pregnancy. Although most cases of pre-eclampsia are mild and cause no trouble, the condition can get worse and be serious for both mother and baby.
The more severe the condition and the earlier it appears, the greater the risks for you and your baby. Most women who get preeclampsia develop a mild version near their due date, and they and their babies do fine with proper care.
But when preeclampsia is severe, it can affect many organs and cause serious or even life-threatening problems. Preeclampsia causes the blood vessels to constrict, resulting in high blood pressure and a reduced blood flow that can affect organs in your body, such as your liver, kidneys, and brain.
When less blood flows to your uterus, it can mean problems for your baby, such as poor growth, too little amniotic fluid, and placental abruption (when the placenta separates from the uterine wall before delivery). In addition, your baby may suffer the effects of prematurity if you need to deliver early to protect your health. It can cause fits (seizures) in the mother, which is called eclampsia and also affect the baby’s growth. The seizures may be preceded by symptoms such as severe or persistent headache, vision changes (blurred vision, seeing spots, or sensitivity to light), mental confusion, or intense upper abdominal pain. Sometimes, though, the seizures occur without warning.
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 make sure that your blood pressure remains under control. Having check-ups with your antenatal team is the best way of monitoring your condition. You should be offered additional antenatal appointments based on your needs and the needs of your baby.
You should keep active and get some physical activity each day, such as walking or swimming. Eat a healthy, balanced diet and keep your salt intake low, as this can reduce blood pressure.
You may have heard that some supplements, such as garlic, might prevent high blood pressure. The truth is that there isn’t enough evidence to show that they are effective, and they are not recommended as a means of preventing high blood pressure in pregnancy.
For most anti-hypertensive drugs, there is limited information on whether they pass into breast milk or whether they may have any effect on a breastfed baby. Talk to your midwife or doctor about breastfeeding if you’re taking medication.