Blood pressure is the least interesting thing that happens at an antenatal appointment and the most important. It takes thirty seconds, nobody explains the numbers, and it is the check that catches the condition responsible for most of the genuine emergencies in the second half of pregnancy.
Pre-eclampsia usually produces no symptoms at all until it is well advanced. That single fact explains the whole design of antenatal care — why appointments get closer together towards the end, why a urine sample is taken every time, and why "I feel fine" is not evidence of anything.
The short answer, and the part that matters most: 140/90 mmHg or above is high blood pressure in pregnancy; 160/110 or above is severe and needs same-day assessment. Call your midwife or maternity unit the same day if you have a severe headache, visual disturbance, pain below the ribs, vomiting in the second half of pregnancy, or sudden swelling of the face and hands. Most pre-eclampsia has no symptoms, which is why every appointment includes blood pressure and a urine test.
The numbers
| Reading | What it is called | What follows |
|---|---|---|
| Below 140/90 | Normal range | Routine checks continue |
| 140/90 – 159/109 | Hypertension | Repeat measurement, urine testing, blood tests; treatment offered above 140/90 if not already on medication |
| 160/110 or above | Severe hypertension | Same-day assessment, usually in hospital |
| Raised BP + protein in urine | Pre-eclampsia | Specialist care and a plan for monitoring and timing of birth |
NICE also sets a target for treated hypertension in pregnancy of 135/85 mmHg, tightened from the older 150/100. If you are on medication and were given the older target, that is worth raising at your next appointment.
Blood pressure does not sit still across pregnancy. It typically falls a little through the middle trimester as blood vessels relax, then climbs back towards pre-pregnancy levels near term. A reading that has risen 20 points from your own baseline can be more informative than the same number in someone else, which is another argument for having a baseline at all.
What pre-eclampsia actually is
It is a disorder of the placenta that shows up as a disorder of your blood vessels. New high blood pressure after 20 weeks, together with protein in the urine or evidence that another organ is affected, is what defines it.
The consequences are what make it serious rather than the numbers: it can restrict the baby's growth, damage the liver and kidneys, affect clotting, and progress to eclampsia — seizures. The only definitive treatment is delivery, which is why the whole management of pre-eclampsia is a running calculation about timing.
Feeling well is not reassurance. By the time pre-eclampsia produces symptoms it is usually advanced. This is the opposite of most conditions, and it is why the least eventful part of an antenatal appointment is the part that must not be skipped.
The warning signs, in the order they matter
🚨 Any of these — same day, not tomorrow
- Severe headache that does not settle with paracetamol
- Visual disturbance — flashing lights, blurred vision, spots, or double vision
- Pain just below the ribs, usually on the right side — often mistaken for indigestion
- Vomiting in the second half of pregnancy, when it is not morning sickness
- Sudden swelling of the face, hands or feet — the suddenness is the signal
- Reduced fetal movements, which can accompany a failing placenta
Pain under the ribs is the one most often ignored, because it feels like heartburn and heartburn is universal in late pregnancy. Our guide to heartburn relief covers the ordinary kind; pain that is sharp, on the right, and not related to eating is a different thing and needs a phone call. Similarly, ordinary swollen feet and ankles are common and benign — it is sudden swelling, and swelling of the face and hands, that matters here.
Aspirin: the prevention nobody mentions
Low-dose aspirin genuinely reduces the risk of pre-eclampsia, and NICE is specific about who should be offered it: 75–150 mg daily from 12 weeks until birth for anyone with one high-risk factor, or with more than one moderate risk factor.
| High risk — any one is enough | Moderate risk — more than one is enough |
|---|---|
|
Chronic (pre-existing) hypertension Hypertension or pre-eclampsia in a previous pregnancy Chronic kidney disease Type 1 or type 2 diabetes Autoimmune disease such as lupus or antiphospholipid syndrome |
First pregnancy Age 40 or over BMI of 35 or more at booking Pre-eclampsia in your mother or sister A multiple pregnancy More than 10 years since your last pregnancy |
If you have any of these and aspirin has not been mentioned, raise it. It is one of the few genuinely preventive interventions in antenatal care, it is cheap, and it is frequently missed — which is why NICE has a quality standard specifically about assessing this risk at booking.
Measuring at home
A series of home readings is more useful to a clinician than a single clinic measurement taken after you have rushed in from a car park. If you monitor at home:
- Use an upper-arm cuff validated for use in pregnancy. Wrist devices are less reliable, and some validated-for-adults monitors perform poorly in pregnancy and in pre-eclampsia specifically.
- Sit still for five minutes first, feet flat, back supported, arm at heart height.
- Take readings at the same time of day and write down all of them, not just the alarming ones.
- Do not self-adjust medication on the basis of home readings.
- Bring the record — the trend is what changes decisions.
Home monitoring supplements antenatal appointments and does not replace them, because the urine test and the fundal height measurement only happen in the clinic.
If pre-eclampsia is diagnosed
Care moves to a specialist team. That usually means more frequent blood pressure checks, blood tests for liver, kidney and platelet function, growth scans with umbilical artery Doppler, and a conversation about when the baby should be born. Medication controls blood pressure but does not treat the underlying condition.
Where the pregnancy is preterm, the balance between the risks of prematurity and the risks of continuing is reassessed constantly, sometimes daily. Our guide to fetal growth percentiles covers the scans that accompany that decision, and the antenatal appointment schedule shows where the routine checks sit around it.
After birth
Pre-eclampsia does not always end with delivery. Blood pressure can stay high or rise in the days afterwards, and pre-eclampsia can appear for the first time postnatally — which is why the warning signs above are worth carrying for at least six weeks after birth. Our postpartum recovery guide covers what else to watch for in that period.
When to call, restated
Call your midwife or maternity unit the same day if: you have a severe headache, visual disturbance, pain below your ribs, vomiting in the second half of pregnancy, sudden swelling of the face or hands, a home blood pressure reading of 140/90 or above, or reduced fetal movements after 24 weeks. Go to hospital immediately for a reading of 160/110 or above, or if a headache comes with visual changes and vomiting together. Nobody will consider this a wasted call.
Frequently Asked Questions
What is normal blood pressure in pregnancy?
Broadly the same as outside pregnancy. 140/90 mmHg or above is the threshold for hypertension, and NICE recommends offering treatment above that if you are not already on medication. 160/110 or above is severe and needs same-day assessment. Blood pressure normally dips slightly in the middle of pregnancy and rises back towards term, which is why a single reading matters less than the pattern.
What are the warning signs of pre-eclampsia?
A severe headache that does not settle; visual disturbance — flashing lights, blurring, spots; pain just below the ribs, usually on the right; vomiting in the second half of pregnancy; and sudden swelling of the face, hands or feet. Any of these needs assessment the same day. Most pre-eclampsia produces no symptoms at all until it is advanced, which is exactly why blood pressure and urine are checked at every appointment.
Who should take aspirin in pregnancy?
NICE recommends 75–150 mg of aspirin daily from 12 weeks until birth for anyone with one high-risk factor — such as chronic hypertension, previous pre-eclampsia, kidney disease, diabetes or an autoimmune condition — or with more than one moderate risk factor, such as a first pregnancy, age 40 or over, a BMI of 35 or more, a family history of pre-eclampsia, or a multiple pregnancy. It is a genuinely effective preventive measure and is often not discussed.
Why is my urine tested at every appointment?
Because protein in urine alongside raised blood pressure is what converts "high blood pressure in pregnancy" into a diagnosis of pre-eclampsia. The dipstick is a screen; if it is positive the sample is quantified properly. It also picks up urine infections, which are common in pregnancy and need treating promptly.
Can I monitor my blood pressure at home?
Yes, and a record over weeks is far more useful to a midwife than a single reading taken in a waiting room after you have hurried in. Use an upper-arm cuff validated for pregnancy rather than a wrist device, sit still for five minutes first, and take readings at the same time of day. Home monitoring supplements appointments and does not replace them.
What is white coat hypertension?
A reading that is high in a clinic and normal at home, caused by the clinic itself. It is common and it matters, because it can lead to treatment that is not needed — which is one of the reasons home readings are worth bringing. It is not a reason to dismiss a high clinic reading; it is a reason to measure again properly.
Does pre-eclampsia go away after birth?
Usually, but not immediately, and not always straight away. Blood pressure can stay high or even rise in the first days after delivery, and pre-eclampsia can appear for the first time postnatally. This is why the warning signs are worth knowing for at least six weeks after birth, not only during pregnancy.
Does swelling always mean pre-eclampsia?
No. Swollen feet and ankles are extremely common and usually mean nothing more than fluid and gravity. What matters is the pattern: swelling that comes on suddenly, or that involves the face and hands rather than the feet, or that arrives alongside a headache or visual changes, is the kind that needs assessing the same day.
Blood pressure and pre-eclampsia — at a glance
Hypertension in pregnancy means a reading of 140/90 mmHg or above; 160/110 or above is severe and needs same-day assessment, and the treatment target once on medication is 135/85. Pre-eclampsia is new hypertension after 20 weeks with protein in the urine or another organ affected, and it usually causes no symptoms until it is advanced — which is why blood pressure and urine are checked at every single appointment. The warning signs that need a same-day call are severe headache, visual disturbance, pain below the ribs, vomiting in late pregnancy, sudden swelling of the face and hands, and reduced fetal movements. Aspirin at 75–150 mg daily from 12 weeks meaningfully reduces the risk for anyone with one high-risk factor or more than one moderate one, and it is frequently not offered. It can also appear for the first time after birth.
Inside Baby Novum: blood pressure and pulse are logged with a dated history and chart, and the swelling tracker records it by body zone — which is what makes "sudden" visible rather than remembered. Appointment reminders sit in the same calendar, so the readings and the visit they belong to are in one place, on the phone, with no account and no server.