High blood pressure, pre-eclampsia and HELLP

What is high blood pressure in pregnancy?

An ideal blood pressure is between 90/60 and 120/80. High blood pressure is a reading of more than 140/90 when measured by a health professional, or 135/85 when measured at home. The higher number is when the heart is contracting and pumping blood, and the lower when it relaxes between heartbeats (Blood Pressure UK, no date; NHS 2024).

One in ten pregnant women and people have raised blood pressure, either as a pre-existing condition or arising in pregnancy. On its own, raised blood pressure can be treated with medication, which reduces the risk of complications and is considered safe for the baby (Action on Pre-eclampsia, 2025; NHS, 2024).

There may be no symptoms of high blood pressure, but anyone who notices the following should mention it to a health professional as soon as possible (Blood Pressure UK, no date; NHS, 2024):

• Blood-shot eyes
• Blurred vision
• Chest pain
• Feeling sick or unwell

Action on Pre-eclampsia has a useful decision aid for anyone who wishes to understand more about the risks of high blood pressure before discussing it with a doctor.

What is pre-eclampsia?

Pre-eclampsia [pre-ek-lamp-sia] is a complication of pregnancy which affects the placenta and can lead to high blood pressure and problems with the baby's growth. It can cause serious complications if it is not monitored and treated (Action on Pre-eclampsia, 2024 a; NHS, 2026).

It can happen at any time in pregnancy but usually appears in the second half of pregnancy. It can also present up to four weeks after the baby is born (Action on Pre-eclampsia, 2024 b; NHS, 2026).

Pre-eclampsia affects up to 5 in 100 pregnancies (so 95 in 100 are not affected) (Giannubilo et al, 2024). 

There is currently no test that can accurately predict if a mother or birthing person will develop pre-eclampsia (Gov.uk, 2023).

What does HELLP syndrome mean?

A serious complication of pre-eclampsia is HELLP syndrome, a combined liver and blood clotting disorder. HELLP syndrome stands for haemolysis (H), elevated liver enzymes (EL) and low platelet count (LP). It is more common than eclampsia (below) but can be harder to diagnose (Action on Pre-eclampsia, 2024 c).

What is eclampsia?

Rarely, pre-eclampsia becomes eclampsia, and the woman or birthing person has a seizure (NHS, 2026). This is where the body twitches involuntarily in repetitive, jerky movements.

Eclampsia can happen up to 23 days after birth. Most women and birthing people make a full recovery (Action on Pre-eclampsia, 2024 b).

What are the warning signs of pre-eclampsia?

During routine antenatal appointments, the midwife will check blood pressure and urine (wee) to look out for (NHS, 2026):

• High blood pressure
• High levels of protein in the urine

These can appear weeks before any other signs of pre-eclampsia, and while the pregnant woman or person feels completely well (NHS, 2026).

Sometimes, the mother or birthing person might be the first to notice signs of pre-eclampsia (NHS, 2026):

• Sudden swelling in the ankles, face, feet and hands
• A severe headache that doesn’t go away with painkillers
• Problems with vision, such as blurred vision or seeing flashes
• Pain below the ribs on the right side (over the liver)
• Heartburn that doesn’t go away with heartburn medicine
• Vomiting
• Feeling very unwell

How is pre-eclampsia treated?

If pre-eclampsia is diagnosed, the mother or birthing person will be referred to a doctor for an assessment (NHS, 2026).

Women and birthing people with high blood pressure will be offered extra antenatal appointments. They will also be offered more scans during the pregnancy to check the baby’s growth. Medication will be offered to reduce blood pressure and the chance of a stroke (NICE, 2023; NHS, 2026).

If the condition is severe the recommendation will be to stay in hospital (NICE, 2023; NHS, 2026).

Pre-eclampsia will not go away while the woman or birthing person remains pregnant. It goes away within hours or up to six months after the birth (Action on Pre-eclampsia, 2024 b).

Does pre-eclampsia affect birth?

The doctor will discuss timing of the birth with the mother or birthing parent. Birth will be recommended early, usually from 37 weeks of pregnancy but in some cases earlier. An induction or caesarean birth might be offered. Both the woman and pregnant person, and the baby will be monitored throughout (NHS, 2026; NICE, 2023).

A recent review of evidence suggests that birth from as early as 34 weeks reduces complications for the mother or birthing person. These complications could include HELLP syndrome or admission to the high dependency unit (Beardmore-Gray et al, 2026).

Early birth did not affect the chance of caesarean birth. There was no clear effect on the rate of neonatal admission and reviewers concluded that it probably reduces the chance of stillbirth, though this remains uncertain (Beardmore-Gray et al, 2026).

How might pre-eclampsia affect the baby?

The baby may get less oxygen and nutrients as the mother or birthing person’s blood supply to the placenta is reduced. This can lead to slower growth, and in very severe cases, stillbirth (Action on Pre-eclampsia, 2024 a).

What happens after the baby is born?

Following pre-eclampsia, the pregnant woman or person may need to stay in hospital for longer than usual after the birth. This is until their blood pressure has been controlled for 24-48 hours (Action on Pre-eclampsia, 2024 b).

After returning home, their blood pressure will be monitored by a community midwife or GP until it settles. A medical review should be offered at the 6-8 week GP check (Action on Pre-eclampsia, 2024 b).

Treatment for high blood pressure can be adapted so that breastfeeding is safe, and medication is easier to take once a day (NICE, 2023). 

Serious complications are very rare. With the right treatment and where no permanent damage occurs, the mother and birthing person, and baby should make a full recovery (Action on Pre-eclampsia, 2024 c).

What are the signs of HELLP?

The typical symptoms of HELLP are (Action on Pre-eclampsia, 2024 c):

• Very severe right-side pain below the ribs, sometimes misdiagnosed as heartburn or gall bladder pain
• Sometimes with vomiting, headaches, and other signs of pre-eclampsia

How is HELLP/eclampsia treated?

Most mothers and birthing parents have a full recovery within days. Any impact on the baby is related to either prematurity or restricted growth because of the effect on the placenta (Action on Pre-eclampsia, 2024 c).

About one person in 20 experiences HELLP again in their next pregnancy, and 19 in 20 will not. Pre-conception counselling may be available, and the next pregnancy will be considered at higher risk (Action on Pre-eclampsia, 2024 c).

What increases the likelihood of pre-eclampsia?

Several factors increase the chance of pre-eclampsia. They are (NHS, 2026; NICE 2023):

• A previous history of pre-eclampsia or high blood pressure during pregnancy
• Chronic medical conditions, such as high blood pressure, diabetes or kidney disease before becoming pregnant
• Autoimmune conditions such as lupus or antiphospholipid syndrome. Lupus is more common in people of Asian, Black African and Black Caribbean ancestry compared with white populations (Lupus UK, 2025).

Some factors slightly increase the risk (Hurnme et al, 2025; Giannublilo et al, 2024; NICE, 2023; NHS, 2026):

• Being pregnant with a first baby, or more than 10 years since the last baby
• First baby with current partner
• If the baby’s father has fathered a previous pre-eclamptic pregnancy
• Being over 40 years old
• Being from a Black or South Asian ethnic background
• Expecting twins or triplets
• A family history of pre-eclampsia (the mother or birthing parent’s mother or sister)
• A body mass index (BMI) of 35 or more before pregnancy

Reducing the chance of pre-eclampsia

If the mother or birthing person is at an increased risk of pre-eclampsia, they might be advised to take a low dose of aspirin daily (75-150mg). This will be from the 12th week of pregnancy until the baby is born (NHS, 2026; NICE, 2023).

Aspirin should only be taken when advised by a midwife or doctor (NHS, 2026; NICE, 2023).

Maintaining a healthy weight and exercise can help lower the risk of pre-eclampsia (NHS, 2026). 

Where can I find support?

Action on Pre-eclampsia (APEC) offers support and information for those affected by pre-eclampsia. This information is available in several languages. There is a helpline available, call 01386 761 848. 

Our friends at Action on Pre-eclampsia kindly reviewed and contributed to this article.

Women and birthing people (and their partners) who have been through severe pre-eclampsia may be more likely to experience post-traumatic stress disorder (PTSD) and postpartum depression.

Speak to the GP or midwife if pre-eclampsia is leading to anxiety or depression.