PHILA TODAY · LIVE WELL · EAT WELL · MOVE WELL
HIGH BLOOD PRESSURE SERIES · ARTICLE 11 OF 12
High blood pressure in pregnancy
Pre-eclampsia and what to watch for.
High blood pressure in pregnancy is a different conversation to high blood pressure in the rest of life. The numbers move faster. The consequences are bigger, both for the mother and the baby. The medications are different. And the single biggest factor that determines a good outcome — far more than any tablet — is being booked into antenatal care early.
This article is for women who are pregnant, who are planning a pregnancy, or who have a pregnant partner, daughter, sister or friend. It explains the four kinds of pregnancy BP problems, what pre-eclampsia is and why it is so dangerous, the warning signs that need a same-day clinic visit, what tests to expect at each antenatal stage, and what treatment looks like — both during pregnancy and afterwards.
If you remember nothing else
Book antenatal care before week 12 of pregnancy if you can. Carry your antenatal card with you at every visit and in any emergency. And learn the four pre-eclampsia warning signs in the next section. They could save your life or your baby’s.
Why BP in pregnancy is different
A normal pregnancy lowers blood pressure for most of the first half. By around 20 weeks, BP starts to drift back up to its pre-pregnancy level. The body is doing extraordinary things — growing a whole new circulation, including the placenta — and BP is one of the systems that has to adjust.
When something goes wrong with that adjustment, BP rises beyond normal. In the worst cases, the placenta itself starts to malfunction, which affects blood flow to the baby. This is why pregnancy BP problems are urgent in a way that everyday BP is not — they affect two people, one of whom (the baby) has very little reserve.
South Africa has one of the higher maternal-mortality rates in middle-income countries, and BP-related problems are one of the top three causes. The good news is that most of these deaths are preventable with early booking, regular monitoring, and prompt response to warning signs.
The four kinds of pregnancy BP problems
1. Chronic hypertension
BP that was high before pregnancy, or that is found to be high before 20 weeks. About 1 in 30 South African women starting pregnancy already has chronic hypertension, often undiagnosed.
Treatment continues through pregnancy, but the choice of medication usually changes (see below). Women with chronic hypertension have a higher chance of developing pre-eclampsia on top of their existing BP problem.
2. Gestational hypertension
BP that becomes high during pregnancy, usually after 20 weeks, but without protein in the urine and without organ damage. About 1 in 15 South African pregnancies develops this.
Gestational hypertension usually goes away within 6 – 12 weeks after delivery. But around 1 in 4 women with gestational hypertension goes on to develop pre-eclampsia in the same pregnancy, so close monitoring is essential.
3. Pre-eclampsia
The most dangerous of the four. High BP (above 140 / 90) plus either protein in the urine, or signs of organ damage (kidneys, liver, brain, blood), developing after 20 weeks of pregnancy.
Pre-eclampsia affects about 1 in 20 South African pregnancies. It is the single biggest cause of premature delivery and stillbirth in this country. It can also progress to eclampsia — full-blown seizures — which is a medical emergency.
The cause is incompletely understood but seems to involve abnormal development of the placenta in early pregnancy, with consequences that only appear in the second half. The only definitive treatment is delivery of the baby.
4. Chronic hypertension with superimposed pre-eclampsia
A woman who already has chronic hypertension develops the signs of pre-eclampsia on top. This is more common than people realise — about 1 in 4 women with chronic hypertension goes on to have superimposed pre-eclampsia. The treatment urgency is the same as for pre-eclampsia.
Pre-eclampsia — the four warning signs to know
Pre-eclampsia rarely arrives without warning. The warning signs are specific and worth memorising — by every pregnant woman, every partner, and every family member. These are the symptoms that need a same-day clinic or hospital visit.
Same-day clinic visit if you are pregnant and have ANY of these
• A severe, persistent headache that doesn’t go away with paracetamol and a glass of water.
• Vision changes — blurred sight, double vision, flashing lights or floaters, sudden spots or darkness in your visual field.
• Severe pain in the upper right of your abdomen, just under your ribs — this is liver pain, not heartburn, and is one of the most specific signs.
• Sudden, severe swelling — particularly of the face, hands or eyelids — appearing over a few days. (A small amount of ankle swelling toward the end of the day is normal in pregnancy. Sudden facial swelling is not.)
Other signs that should prompt a call to your antenatal clinic include:
• Rapid weight gain — more than 1 kg in a week or 3 kg in a month
• Feeling generally unwell, nauseated, or short of breath without explanation
• A noticeable reduction in your baby’s movements
• A home BP reading above 140 / 90 if you are measuring at home
Get to a hospital immediately if
You have a seizure (fit). Call 10177. This is eclampsia.
You have severe abdominal pain that is constant and not relieved by changing position — this could be placental abruption or HELLP syndrome.
You have a sudden severe headache with vomiting or weakness on one side of the body — possible stroke.
You have heavy bleeding or sudden loss of fluid from the vagina, particularly with pain.
Who is at higher risk of pre-eclampsia
Pre-eclampsia can happen to anyone, but some women are at substantially higher risk. Knowing where you sit on this list determines how closely you should be monitored:
• First pregnancy. The risk is highest in a first pregnancy and falls in later pregnancies (with the same partner).
• Pre-existing high BP, kidney disease, or diabetes. Any one of these doubles or triples the risk.
• A previous pregnancy complicated by pre-eclampsia. Roughly 1 in 5 of these women will get it again.
• Twin (or multiple) pregnancy. The risk is about double.
• Family history — mother or sister with pre-eclampsia.
• Maternal age under 20 or over 35.
• Obesity — BMI over 30 at the start of pregnancy.
• Long gap between pregnancies — more than 10 years.
• Black South African or African ancestry — somewhat higher risk and often more severe disease.
If two or more of these apply to you, your antenatal clinic will usually prescribe low-dose aspirin (usually 75 – 150 mg daily) from 12 weeks of pregnancy onward. This has been shown in large trials to reduce pre-eclampsia risk by about 25%. It is one of the best-evidenced preventive treatments in obstetrics.
What antenatal care should look like
South African public-sector antenatal care is one of the success stories of the health system. Every visit is built around catching exactly the problems in this article early. A typical schedule for a healthy pregnancy:
Pregnancy stage What happens at each visit First booking (before week 12 if possible) Full BP, urine test, weight, blood tests including HIV and syphilis, ultrasound to date the pregnancy Every 4 weeks until 28 weeks BP, urine for protein, weight, fetal heartbeat, fundal height Every 2 weeks from 28 to 36 weeks Same as above, plus signs of pre-eclampsia and baby’s growth Every week from 36 weeks until delivery Same as above, plus engagement of the baby’s head, position After delivery (6 weeks) Mother’s BP, urine, contraception, and a check that any pregnancy hypertension has resolved
At every visit, two specific tests are looking for pre-eclampsia: your BP and a urine dipstick for protein. If both are normal, you are reassured. If either is abnormal, the rest of the visit becomes about investigating further.
Book early — the single most important thing
The number one predictor of a good pregnancy outcome in South Africa is being booked at an antenatal clinic before 12 weeks. The earlier you are in the system, the earlier any BP problem is caught, the earlier aspirin can be started if needed, and the earlier any growth problem with the baby is identified. Booking is free at all public clinics. You don’t need an appointment for the first visit — just walk in.
Pregnancy-safe BP medication
The five BP drug groups from article 9 are not all safe in pregnancy. Some are excellent. Some are dangerous to the baby. Knowing the difference matters.
Safe and commonly used in pregnancy
• Methyldopa. The most-studied BP drug in pregnancy. Used safely for over 50 years. Still the first-line drug at most South African antenatal clinics. Some women find it makes them feel a little tired or low-mood, but the safety profile for the baby is excellent.
• Labetalol. A beta-blocker that is the other common first-line choice. Often preferred in younger women because it has fewer mood side effects than methyldopa. Generally well-tolerated.
• Nifedipine (long-acting). A calcium channel blocker that is safe and effective in pregnancy. Often added as a second drug if BP is not controlled on methyldopa or labetalol alone.
• Hydralazine. Used in hospital for severe high BP in pregnancy, particularly during labour. Effective and fast-acting.
Avoid in pregnancy
• ACE inhibitors (enalapril, lisinopril, perindopril, etc.) — these damage the baby’s kidneys and can cause stillbirth, particularly in the second and third trimesters.
• ARBs (losartan, telmisartan, etc.) — same risks as ACE inhibitors.
• Most diuretics for primary BP treatment. They are sometimes still used briefly for specific reasons but are not a routine BP choice in pregnancy.
• Atenolol — one specific beta-blocker that is associated with smaller babies. Labetalol is preferred instead.
If you are already on any of these drugs and you become pregnant — or are planning to — your clinic will switch you to a pregnancy-safe option as soon as possible. Do not stop the medication on your own; uncontrolled BP is also a risk. Call your clinic the same day, explain the situation, and they will manage the switch.
Treating severe pre-eclampsia and eclampsia
If pre-eclampsia is severe, or has progressed to eclampsia (seizures), you will be admitted to hospital. Treatment will include:
• Magnesium sulfate. Given by drip, this medication prevents and treats eclamptic seizures. It is one of the most important obstetric medicines in the world and is on the SA Essential Medicines List. Every district hospital has it.
• Faster-acting BP medication. Usually labetalol or hydralazine, given by drip or injection, to bring BP down to a safer range within hours.
• Delivery of the baby — the only definitive treatment for pre-eclampsia. The timing of this is a careful judgement that balances the risks to the mother of staying pregnant against the risks to the baby of being born early. In many cases, magnesium and BP medication can buy 24 – 48 hours, during which the baby receives a steroid injection to mature the lungs faster.
South African maternity care for severe pre-eclampsia is generally good — the protocols are well-established, magnesium is available, and most district hospitals have the capacity to manage early delivery if needed. The biggest preventable problem remains late presentation: a woman in trouble who didn’t recognise the warning signs early enough.
After delivery
BP usually starts to come down within hours of delivery, but can spike higher in the first 1 – 2 weeks postpartum, sometimes for the first time. Your clinic will usually check BP in the first week, at 2 weeks, and again at 6 weeks.
For most women with gestational hypertension or pre-eclampsia, BP returns to normal by 6 – 12 weeks. For some, it doesn’t — which usually means underlying chronic hypertension that the pregnancy had revealed.
Future pregnancies
If you had pre-eclampsia in one pregnancy, you should plan future pregnancies with that history in mind. Tell every antenatal clinician at every visit. You will be offered low-dose aspirin from 12 weeks, you will likely be monitored more closely, and your BP will be a focus from the first visit.
The long view
Women who had pre-eclampsia, gestational hypertension, or gestational diabetes are at about double the long-term risk of developing chronic high BP, Type 2 diabetes, and cardiovascular disease over the next 20 years. This is not destiny — it is information. Annual BP and blood sugar checks, healthy lifestyle, and ideally a contraceptive plan that doesn’t push BP up (some combined pills do) are all part of looking after yourself in the years afterwards.
If you had any form of pregnancy hypertension, you should be reading the rest of this series too. Articles 4 through 8 — measurement, food, salt, walking, sleep — are particularly relevant.
The bigger picture
Pregnancy is the most carefully monitored period of an adult woman’s medical life in South Africa, and that is exactly because problems like pre-eclampsia can develop quickly and have serious consequences. The system is built to catch them. Your job is to be inside the system early, attend the visits, learn the four warning signs, and call when something is wrong.
Most pregnancies complicated by high BP, even severe pre-eclampsia, end well in South Africa today. The mothers go home. The babies grow up. The medical attention that pregnancy hypertension demands is sometimes inconvenient, sometimes frightening, but almost always effective when started in time.
The final article in the series steps back from any single condition and takes the long view — what living well with high blood pressure actually looks like over years and decades, the four anchors of sustainable BP management, and why the small daily acts add up to a long, full life.
Where to get more help
Your nearest public antenatal clinic — free, no appointment needed for the first booking visit, comprehensive care including BP monitoring.
Mom Connect — South African Department of Health pregnancy SMS service. Free, weekly information from pregnancy onwards. Register at any antenatal clinic.
Heart and Stroke Foundation South Africa — heartfoundation.co.za · 021 422 1586.
Phila Today Diabetes Series — Article 14 covers diabetes in pregnancy, which often travels with BP problems.
Phila Today High Blood Pressure Series — next, and final: living well with high blood pressure — the long view.
Phila Today · Article 11 of 12 in the High Blood Pressure Series