Eclampsia is the gravest form of pregnancy-induced hypertension. It occurs when a pregnant person with a hypertensive disorder develops sudden seizures with no other neurological explanation. Eclampsia is life-threatening for both mother and baby, and in low- and middle-income countries, preeclampsia and eclampsia together account for 10% to 15% of all direct maternal deaths.
The Spectrum of Pregnancy Hypertension
Pregnancy-induced hypertension exists on a spectrum. It begins with gestational hypertension, which is elevated blood pressure developing after 20 weeks of pregnancy without other organ involvement. When that high blood pressure starts damaging organs, it becomes preeclampsia. Preeclampsia with severe features is diagnosed when blood pressure reaches 160/110 mmHg or higher, or when signs of kidney injury, liver dysfunction, dangerously low platelet counts, or neurological symptoms appear.
Eclampsia sits at the far end of this spectrum. It is a severe complication of preeclampsia defined by the onset of generalized tonic-clonic seizures. These are full-body convulsions involving muscle stiffening followed by rhythmic jerking, loss of consciousness, and sometimes stopped breathing. The seizures can happen before, during, or after delivery.
What Causes the Seizures
The root problem in eclampsia is poor blood flow to the placenta, which triggers a cascade of damage to blood vessels throughout the body. Two leading theories explain how this ultimately reaches the brain.
In the first, the brain’s blood vessels overreact to rising blood pressure by clamping down too tightly. This vasospasm starves brain tissue of oxygen, causing swelling (both from cell injury and from fluid leaking out of damaged vessels) that can provoke seizures. Brain imaging of eclamptic patients has confirmed areas of spasm consistent with this pattern.
In the second theory, the opposite happens: blood pressure rises so fast that it overwhelms the brain’s ability to regulate its own blood flow. Tiny arteries lose their protective constriction, and the barrier between blood and brain tissue breaks down. Fluid and damaging proteins flood into surrounding tissue, compressing the brain inside the rigid skull. This compression produces the classic warning signs of headache, nausea, vomiting, visual disturbances, and ultimately convulsions. Research has found that this barrier breakdown alone, even without other factors, is enough to trigger seizure activity. The resulting pattern of swelling, concentrated in the back of the brain, is now recognized as posterior reversible encephalopathy syndrome (PRES).
Warning Signs Before a Seizure
Eclamptic seizures rarely strike without warning. Visual symptoms affect up to 25% of patients with severe preeclampsia and roughly 50% of those who go on to develop eclampsia. Blurred vision is the most common complaint, but other signs include flashing lights (photopsia), blind spots, sudden difficulty focusing, and in severe cases, complete blindness. Cortical blindness, caused by swelling in the visual processing area at the back of the brain, occurs in 1% to 15% of severe cases and can precede seizures by four to seven hours.
Beyond vision changes, a severe headache that doesn’t respond to typical pain relief, upper abdominal pain (especially under the right ribs, where the liver sits), sudden nausea or vomiting, and confusion or agitation are all red flags. Any of these symptoms in a person with known high blood pressure during pregnancy warrants immediate medical evaluation.
HELLP Syndrome: A Related Emergency
HELLP syndrome is a dangerous variant that can occur alongside or independently of eclampsia. The name stands for hemolysis (red blood cells breaking apart), elevated liver enzymes, and low platelets. It is diagnosed when blood tests show all three problems simultaneously: evidence of red blood cell destruction, liver enzyme levels more than double the normal upper limit, and platelet counts below 100,000 cells per microliter.
HELLP can develop rapidly, sometimes before blood pressure is dramatically elevated, which makes it easy to miss. Its symptoms, particularly upper abdominal pain and nausea, overlap with common pregnancy complaints. When HELLP and eclampsia occur together, the risk of serious complications like liver rupture, stroke, and organ failure climbs significantly.
How Eclampsia Is Treated
The first priority during an eclamptic seizure is preventing injury and stopping the convulsion. Magnesium sulfate is the standard treatment, considered superior to other anti-seizure medications for this specific condition. It is given intravenously as a loading dose over 20 to 30 minutes, followed by a continuous low-dose infusion maintained for 24 hours after delivery. If seizures recur, an additional bolus is given and the infusion rate is increased.
Delivery is the only cure. Eclampsia itself is considered a clear indication for delivery regardless of gestational age. Whether labor is induced or a cesarean section is performed depends on several factors: how far along the pregnancy is, how stable the mother’s condition is, and how favorable the cervix is for vaginal delivery. In some cases of severe preeclampsia at or before 34 weeks, induction of labor is still a reasonable option if conditions allow. After delivery, symptoms typically begin to resolve, though close monitoring continues because seizures can occur in the postpartum period as well.
Risks to Mother and Baby
Seizures in eclampsia can cause stroke, brain hemorrhage, brain swelling severe enough to cause herniation (where tissue is forced out of its normal position), and lasting neurological damage. Beyond the immediate crisis, research shows that eclamptic seizures can predispose a person to epilepsy and cognitive impairment later in life.
Maternal mortality varies widely depending on the healthcare setting. Studies from referral hospitals have reported death rates ranging from 0.5% to over 11%, with lower-resource settings seeing consistently worse outcomes. Postpartum hemorrhage is also a frequent complication, affecting more than half of patients with severe preeclampsia or eclampsia in some studies. For the baby, the risks include oxygen deprivation during seizures, premature birth from emergency delivery, and growth restriction from the underlying placental dysfunction that drives the disease.
Who Is Most at Risk
Eclampsia most commonly develops from pre-existing preeclampsia, so the risk factors overlap. First pregnancies, pregnancies in people over 35 or under 20, carrying multiples, obesity, chronic high blood pressure, diabetes, kidney disease, and a personal or family history of preeclampsia all raise the likelihood. Having had preeclampsia in a previous pregnancy is one of the strongest predictors.
What makes eclampsia particularly dangerous is its unpredictability. While most cases arise from recognized preeclampsia, seizures occasionally occur in people whose blood pressure was only mildly elevated or whose condition hadn’t yet been flagged as severe. This is why routine blood pressure monitoring and urine testing throughout pregnancy exist: catching the earlier stages of the disease is the most effective way to prevent its gravest form.