Pre-eclampsia warning signs in pregnancy

Q: From what point in pregnancy can pre-eclampsia develop?

Pre-eclampsia usually develops after 20 weeks of pregnancy. In some cases it can appear shortly after birth. It does not happen in the first half of pregnancy.

Q: Can you have pre-eclampsia without any symptoms?

Yes. In its early stages, pre-eclampsia often brings no symptoms you would notice. High blood pressure and protein in your urine, both picked up through routine antenatal checks, are usually the first signs. This is why getting to all your scheduled appointments matters even when you feel well.

Q: Which symptoms mean you should seek help straight away?

Call your midwife, GP surgery, or maternity unit straight away if you develop a severe headache that ordinary painkillers do not ease, problems with your vision such as blurring or flashing lights, severe pain just below your ribs, or sudden swelling of your face, hands, or feet. Do not wait for your next appointment. In an emergency, call 999.

Q: What is the purpose of the urine test at antenatal appointments?

Your urine is checked with a dipstick at every antenatal appointment to look for protein, which can be a sign your kidneys are being affected by pre-eclampsia. If the dipstick shows a certain level of protein, your care team may arrange a more detailed test to measure the amount more precisely.

A woman at a bar, holding a small box with a drink and a straw.

The information in this article is for general informational purposes only and does not substitute for professional medical or dietary advice, particularly during pregnancy. If you are outside the UK, please consult your local doctor, midwife, or healthcare provider for guidance that reflects your country's recommendations.

You can feel completely well while pre-eclampsia is quietly developing, which is part of why its warning signs are so easy to miss in pregnancy. In the early stages it often brings no symptoms you would notice, even as your blood pressure starts to rise. That is why the blood pressure cuff and urine dipstick at each antenatal appointment are how pre-eclampsia is most often picked up. Pre-eclampsia develops after 20 weeks of pregnancy, or sometimes shortly after birth, and shows up as a mix of high blood pressure and protein in your urine.¹

What is pre-eclampsia?

Pre-eclampsia is two things happening at once: high blood pressure (hypertension) and protein in your urine (proteinuria). The exact cause is not fully understood, though it seems to come down to how the placenta develops. When the placenta does not develop as it should, blood flow to it can drop. That affects your baby's growth and can set off a response in your body that raises blood pressure and puts strain on several organs.²

Pre-eclampsia affects up to 8 in 100 pregnancies in the UK, and many cases are mild. Severe pre-eclampsia is less common and develops in a small number of pregnancies.³

Blood pressure and what the numbers mean

High blood pressure is the main thing your midwife or doctor is checking for. A reading of 140/90 mmHg or higher, taken on two separate occasions at least four hours apart, is generally counted as high in pregnancy. One high reading on its own is not enough to confirm anything; the two-occasion rule is there to tell a genuine, lasting rise apart from a one-off. This is the threshold your care team uses, not a number you need to apply to a home monitor yourself.⁴

The other main sign is protein in the urine, which indicates the kidneys may be affected. This is why urine is checked at every antenatal appointment. If the dipstick shows anything worth investigating, your midwife or care team will arrange further testing to get a clearer picture.⁵

Pre-eclampsia warning signs to know

Because early pre-eclampsia brings no symptoms you would feel, there is no way to pick it up at home before it progresses. As it advances, certain symptoms can appear. If you notice any of the following, get medical help straight away and do not wait for your next appointment.

A severe headache that ordinary painkillers do not ease
Problems with your vision, like blurring or flashing lights
Severe pain just below your ribs
Heartburn that does not ease with antacids
Sudden swelling of your face, hands, or feet (different from the gradual ankle swelling that is common in pregnancy)
Feeling very unwell in yourself⁶

Heartburn and swollen feet are common in pregnancy and on their own do not point to pre-eclampsia. What matters is sudden onset, how severe it feels, or several of these signs showing up together. If you are unsure, call your midwife or maternity unit.

Pregnant woman sitting on a couch with her hand on her chest.

Why antenatal appointments are the first line of detection

Because pre-eclampsia can develop without any symptoms you would notice, getting to all your scheduled antenatal appointments matters. Each one includes a blood pressure check and a urine test, there to catch changes before they become serious. These checks are how it is most often spotted at an early, more manageable stage.⁸

Appointments matter, and so does paying attention to how you feel between them. The symptoms above can appear at any time. If they do, contact your midwife or maternity unit that day rather than waiting for your next appointment.

Frequently Asked Questions

From what point in pregnancy can pre-eclampsia develop?

What blood pressure reading is considered high in pregnancy?

Can you have pre-eclampsia without any symptoms?

Which symptoms mean you should seek help straight away?

What is the purpose of the urine test at antenatal appointments?

Sources

[1] Pre-eclampsia Patient Information

Pre-eclampsia develops after 20 weeks of pregnancy, or occasionally shortly after birth, and is defined by a combination of high blood pressure and protein in the urine.
[2] Pre-eclampsia Patient Information

The condition appears to be linked to a problem with how the placenta develops. When the placenta does not develop as it should, blood flow to it can be reduced. This affects the baby's growth and can trigger a response in the body that raises blood pressure and places strain on several organs.
[3] Pre-eclampsia Patient Information

Pre-eclampsia affects up to 8 in 100 pregnancies in the UK and many cases are mild. Severe pre-eclampsia is less common, developing in a small proportion of pregnancies.
[4] Pre-eclampsia

A reading of 140/90 mmHg or higher on two separate occasions at least four hours apart is generally considered high in pregnancy.
[5] The 2019 NICE Guideline on Hypertension in Pregnancy

Protein in the urine signals that the kidneys are being affected. Urine is tested with a dipstick at every antenatal appointment. If the dipstick shows a result of 1+ or more, a further test, a protein:creatinine ratio (PCR) or albumin:creatinine ratio (ACR), may be arranged to measure the level of protein more precisely.
[6] Pre-eclampsia - Patient Information

Early pre-eclampsia produces no felt symptoms. As the condition advances, specific symptoms can develop: a severe headache that simple painkillers do not relieve, vision problems including blurring or flashing lights, severe pain just below the ribs, heartburn that does not improve with antacids, sudden swelling of the face, hands, or feet, and a general feeling of being very unwell.
[7] Pre-eclampsia - Patient Information

The appropriate contact is a midwife, GP surgery, or local hospital's maternity unit. In an emergency, call 999.
[8] Pre-eclampsia Patient Information

Because pre-eclampsia can develop without any symptoms you would notice, attending all your scheduled antenatal appointments is important. Each appointment includes a blood pressure check and a urine test to catch changes before they become serious.