Preeclampsia is a pregnancy condition involving raised blood pressure and effects on other organs. It can develop quickly, it can appear after birth, and regular antenatal checks are how it is caught early.
Preeclampsia is one of the conditions antenatal care exists to catch. It develops in pregnancy, it can affect both mother and baby, and in its early stages it very often causes no symptoms at all. That combination is what makes it serious, and it is also why the blood pressure check and urine sample at every appointment matter more than they appear to.
Most women who develop preeclampsia do well, particularly when it is picked up early and monitored properly. The difficulty is that the warning signs are easy to attribute to ordinary pregnancy: a headache, some swelling, feeling unwell. This guide explains what preeclampsia is, why it happens, what the warning signs actually are, how quickly it can develop, whether it can occur without raised blood pressure, and why the weeks after birth are a period when symptoms should never be ignored.
What Is Preeclampsia?
Preeclampsia is a condition of pregnancy in which raised blood pressure develops alongside evidence that other organs are being affected. It typically appears after the twentieth week and can occur at any point after that, including after the birth.
The classical description involves high blood pressure together with protein in the urine, which signals that the kidneys are under strain. Current practice recognises that preeclampsia can also be diagnosed when raised blood pressure appears with other organ involvement even if there is no protein: abnormal liver blood tests, a falling platelet count, impaired kidney function, fluid on the lungs, neurological symptoms, or a baby whose growth has slowed.
Left unrecognised it can progress. Severe preeclampsia can affect the liver, the clotting system and the brain, and in its most serious form can cause seizures, which is called eclampsia. A related pattern involving the breakdown of red blood cells, raised liver enzymes and low platelets is known as HELLP syndrome. These outcomes are uncommon, and monitoring exists precisely so that they remain so.
The only treatment that ends preeclampsia is delivery of the baby and the placenta. Everything else, including blood pressure medication, is aimed at keeping mother and baby safe until the safest time to deliver.
When in Pregnancy Does Preeclampsia Appear?
By definition preeclampsia occurs from twenty weeks onwards. Raised blood pressure before that point usually reflects pre-existing hypertension rather than preeclampsia, although women with pre-existing high blood pressure can go on to develop preeclampsia on top of it.
Most cases appear in the third trimester, and a large share are diagnosed after thirty-four weeks. When it appears late in pregnancy it is generally less severe, because delivery is a realistic option and the baby is close to term.
Early-onset preeclampsia, meaning before thirty-four weeks, is less common but tends to be more serious. It is more often associated with restricted growth in the baby and with more marked effects on the mother, and it requires a careful balance between the risks of continuing the pregnancy and the risks of delivering prematurely.
It can also begin during labour, or only after the birth. Postpartum preeclampsia is covered in its own section below, because it is the version women are least often warned about. There is one more timing point worth knowing: because preeclampsia can appear at any stage from twenty weeks, a normal blood pressure at your twenty-eight-week appointment tells you about that day only. It does not protect you from developing the condition three weeks later, which is exactly why the checks continue throughout the antenatal follow-up schedule.
What Causes Preeclampsia?
Preeclampsia begins with the placenta. In early pregnancy the placenta embeds into the wall of the womb and remodels the maternal blood vessels supplying it, converting narrow, muscular arteries into wide, low-resistance channels that can deliver a large volume of blood at low pressure. In preeclampsia, this remodelling is incomplete.
The consequence is a placenta that is relatively poorly perfused. Under this stress it releases a range of substances into the mother's bloodstream, including factors that interfere with the normal function of the endothelium, the single-cell lining of every blood vessel in the body.
Once the endothelium is affected, the picture makes sense. Blood vessels constrict, so blood pressure rises. They become leaky, so fluid moves out of the circulation into the tissues, producing swelling. The kidneys, whose filtering membranes are exquisitely sensitive, begin to leak protein into the urine. The liver capsule stretches, causing pain under the ribs. The brain's vessels are affected, producing headache and visual disturbance. Platelets are consumed, and clotting can become abnormal.
This explains why preeclampsia is described as a multi-system condition rather than simply high blood pressure, and why it resolves once the placenta is delivered. What it does not explain is why the initial remodelling fails in some pregnancies and not others. Immune factors, the mother's own vascular and metabolic health, and genetic influences all appear to contribute. Nothing you did or did not do in early pregnancy caused it.
Warning Signs and Symptoms Women Often Miss
In its early stages preeclampsia is usually silent. Many women feel completely well while their blood pressure is climbing, which is the single most important thing to understand about it. Symptoms often appear only once the condition is well established.
When symptoms do occur, they are frequently mistaken for ordinary late-pregnancy discomfort. The ones to know are:
- A headache that is severe, persistent, or does not settle with simple painkillers and rest
- Visual disturbance: blurred vision, flashing lights, spots or shimmering in your field of view, double vision or temporary loss of vision
- Pain just below the ribs, usually on the right side, sometimes mistaken for indigestion or heartburn that will not resolve
- Nausea or vomiting appearing newly in the second half of pregnancy, rather than continuing from early pregnancy
- Sudden swelling of the face, around the eyes, or of the hands and feet, particularly if it comes on over a day or two
- Rapid weight gain over a short period, reflecting fluid retention rather than anything you have eaten
- Feeling generally and unusually unwell, breathless, or simply not right
- A noticeable reduction in your baby's movements
Two of these deserve emphasis because they are so easily explained away. Swelling of the ankles is extremely common in pregnancy and is usually harmless; swelling of the face and hands that appears suddenly is different, and should prompt a check. Pain under the right ribs is very often assumed to be indigestion, but it is one of the more specific signs of liver involvement and should never be dismissed, especially at night or when it wakes you.
Can You Have Preeclampsia Without High Blood Pressure?
This question is asked constantly, and the honest answer has several parts.
Formally, no. Raised blood pressure is part of the diagnostic definition, so a diagnosis of preeclampsia is not made in its complete absence. But that formal answer conceals several situations in which a woman genuinely feels unwell before, or without, an obviously abnormal reading.
The first is timing. Blood pressure can be normal at one appointment and clearly raised days later, and symptoms sometimes precede the rise. A single normal reading is a snapshot, not a guarantee.
The second is your own baseline. If your blood pressure normally runs low, a reading that has climbed substantially from where it usually sits may still fall under the standard threshold while representing a real and significant change for you. This is why booking readings early in pregnancy are recorded: they give your team a personal comparison rather than a population average.
The third is the related conditions. HELLP syndrome can present with the upper abdominal pain, nausea and feeling unwell of severe preeclampsia while blood pressure is only mildly elevated or occasionally normal, with the abnormality showing in blood tests instead. Similarly, protein in the urine can appear before the blood pressure rises in some women.
The practical conclusion is straightforward: symptoms are worth reporting regardless of what your last blood pressure reading was. If you have a persistent headache, visual disturbance or pain under your ribs, the right response is to be assessed, not to reassure yourself because your blood pressure was fine last week.
How Quickly Can Preeclampsia Develop?
Faster than most people expect. Preeclampsia does not always creep up over weeks; it can move from mild to severe over a matter of days, and sometimes within twenty-four to forty-eight hours.
The underlying placental changes have usually been developing quietly since early pregnancy, so by the time blood pressure rises the process has been in motion for months. What varies is how quickly the visible stage progresses once it starts. Some women have mildly raised blood pressure for weeks with nothing else happening. Others go from a completely normal appointment to needing admission within a few days.
Early-onset preeclampsia tends to progress more rapidly than the late-onset form, which is one reason it is watched so closely. HELLP syndrome and eclampsia can also develop rapidly, occasionally without a long preceding period of obvious illness.
This has two practical implications. First, the interval between antenatal appointments is set with this in mind, and it shortens if anything is flagged. If you are asked to come back in three days rather than three weeks, that is the system working, not a sign that something terrible is happening. Second, a reassuring check does not cover the days that follow. If new symptoms appear the day after a normal appointment, they still need reporting. Nobody will consider you a nuisance for calling twice.
Who Is at Higher Risk?
Preeclampsia can occur in any pregnancy, including in women with no risk factors whatsoever, and roughly speaking most cases occur in first pregnancies. Certain factors, however, raise the likelihood, and they are usually divided into higher and moderate risk.
Higher-risk factors include preeclampsia in a previous pregnancy, chronic high blood pressure, chronic kidney disease, type 1 or type 2 diabetes diagnosed before pregnancy, and autoimmune conditions such as lupus or antiphospholipid syndrome.
Moderate-risk factors include a first pregnancy, an interval of ten years or more since your last pregnancy, being aged forty or over, carrying twins or more, a family history of preeclampsia in your mother or sister, and a body mass index of thirty-five or above at booking. Pregnancies conceived through assisted reproduction, including IVF, and those involving egg donation carry a somewhat higher likelihood as well.
Underlying metabolic conditions matter too. Women with insulin resistance, including many with polycystic ovary syndrome, and women who develop gestational diabetes have a modestly increased risk, which is one reason blood sugar and blood pressure are followed together in pregnancy.
Having risk factors does not mean you will develop preeclampsia, and having none does not mean you cannot. What risk assessment does is determine how closely you are monitored and whether preventive measures are recommended from early pregnancy.
Postpartum Preeclampsia: When It Appears After Birth
Most women assume that once the baby is born the risk has passed. It has not. Preeclampsia can appear for the first time after delivery, and this postpartum form is the one most often missed, precisely because attention has shifted entirely to the baby and appointments have become less frequent.
It most commonly develops within the first week after birth, and particularly in the first forty-eight hours, but it can occur up to about six weeks postpartum. It can follow a pregnancy in which blood pressure was entirely normal throughout, and it can follow any type of birth, vaginal or caesarean. Women who had preeclampsia during pregnancy can also find their blood pressure worsens for several days after delivery before it improves.
The symptoms are the same as in pregnancy: severe or persistent headache, visual disturbance, pain under the right ribs, nausea and vomiting, sudden swelling, breathlessness, or simply feeling profoundly unwell. The difficulty is that all of these are easy to attribute to the aftermath of birth. Exhaustion, headaches, aching, swollen ankles and feeling terrible are so ordinary in the first postnatal week that a genuinely dangerous headache can be brushed aside as tiredness.
Treat any of the following in the six weeks after birth as a reason to be assessed the same day: a headache that will not shift, changes to your vision, pain under your ribs, sudden swelling of your face or hands, breathlessness, or a seizure, which requires emergency care immediately. If you have a blood pressure monitor at home, take a reading, but do not let a borderline number talk you out of seeking help when you feel unwell.
It is worth saying this to whoever is around you in those first weeks, so that someone other than you is watching for it at a time when you are exhausted and unlikely to advocate for yourself.
How Preeclampsia Is Diagnosed and Monitored
Detection is built into routine antenatal care. Blood pressure is measured at every appointment, and urine is tested for protein. These two simple checks, repeated over months, are what allow the condition to be caught while women still feel well.
If blood pressure is raised, it is usually repeated after a period of rest to exclude an artefact of rushing to the clinic. If it remains elevated, the urine sample is quantified more precisely in the laboratory rather than by dipstick alone, and blood tests are taken to look at kidney function, liver enzymes, the full blood count and platelet numbers. Specialised blood tests measuring placental growth factors can help clarify how likely preeclampsia is when the picture is uncertain.
Attention then turns to the baby. An ultrasound assesses growth and the volume of fluid around the baby, and a Doppler study looks at blood flow in the umbilical cord. Fetal heart rate monitoring may be used, and you will be asked to report movements carefully.
Depending on the findings, monitoring may continue as an outpatient with visits every few days, or you may be admitted for closer observation. Medication to lower blood pressure is used to protect you from the effects of hypertension, but it does not treat the underlying condition, and monitoring continues alongside it. If delivery before thirty-four to thirty-six weeks is anticipated, steroid injections are usually given to help the baby's lungs mature.
Timing of delivery is a judgement made jointly, weighing how well you and the baby are against the gestation reached. In milder cases at term, planned delivery is often recommended. In severe cases, delivery may be needed promptly regardless of gestation.
Can Preeclampsia Be Prevented?
Not reliably, and it is important to say so plainly. There is no diet, supplement or lifestyle regimen that removes the possibility. What does exist is a small number of measures that reduce the likelihood in women identified as being at increased risk.
The most firmly established is a low dose of aspirin, usually started from around twelve weeks of pregnancy and continued until close to delivery, recommended for women with one high-risk factor or two or more moderate-risk factors. This is a decision for your doctor to make with you, based on your individual assessment, and is not something to begin on your own initiative. Calcium supplementation is advised in some settings where dietary calcium intake is low.
Beyond that, the useful ground is general and unglamorous. Entering pregnancy with pre-existing conditions well controlled makes a difference, as does having chronic hypertension, diabetes, kidney disease and thyroid problems reviewed before conception where possible. Regular gentle activity, not smoking, and attending appointments consistently all contribute. Broader women's health assessment before pregnancy is genuinely worthwhile for anyone with a previous complicated pregnancy.
What matters most, though, is not prevention but detection. Since the condition often produces no symptoms until it is advanced, the routine checks are the safeguard. If you develop preeclampsia, this also has implications for your longer-term health: women who have had it carry a higher lifetime likelihood of cardiovascular disease and hypertension, so a blood pressure review some months after birth, and periodically thereafter, is a sensible habit.
Emergency Red Flags: When to Seek Urgent Care
Contact your maternity unit or attend hospital immediately, at any point after twenty weeks of pregnancy or within six weeks of giving birth, if you experience any of the following:
- A severe headache, or any headache that does not respond to simple painkillers
- Visual disturbance: blurring, flashing lights, spots, shimmering or loss of vision
- Pain below your ribs, particularly on the right side
- Vomiting that is new in later pregnancy or after birth
- Sudden swelling of your face, hands or feet
- Shortness of breath, chest pain, or difficulty breathing when lying flat
- Reduced or altered movements from your baby
- A blood pressure reading at home that is markedly higher than usual
- Any seizure, which is a medical emergency requiring an ambulance
Do not wait for your next scheduled appointment, and do not wait to see whether things settle overnight. Preeclampsia is one of the situations in which acting early costs very little and waiting can cost a great deal. Maternity units are used to assessing women who turn out to be fine, and that is exactly how it should be.
If you are unsure whether what you are feeling counts, describe it to your midwife or doctor and let them decide. That judgement is their job, not yours, and no one will think you have overreacted.
References
This article was prepared with reference to the following independent health sources.
- NHS. Pre-eclampsia
- NICHD. Preeclampsia and eclampsia
