Pre-eclampsia: delivery of the baby and placenta as definitive treatment
Pre-eclampsia is new high blood pressure after 20 weeks of pregnancy together with protein in the urine, organ damage or poor placental function, and only delivery removes its cause.
Remember
Blood pressure drugs treat a sign rather than the cause. Because the placenta is the cause, delivery of the baby and placenta is the definitive treatment, as it removes the source of the disease, and its timing is chosen for mother and baby.
Pre-eclampsia is a disease of pregnancy in which new high blood pressure appears after 20 weeks. It comes together with new protein in the urine (proteinuria), damage to another organ, or poor function of the placenta, for example slow growth of the baby.
The disease begins in the placenta, the organ that links the baby's circulation to the mother's. A poorly functioning placenta releases factors that injure the lining of the mother's blood vessels, and this injury is called endothelial dysfunction: the cells lining the vessels stop behaving normally, so the vessels narrow and leak. That raises the blood pressure and can injure organs such as the kidneys.
Because the placenta is the source, the definitive treatment (the treatment that removes the cause) is delivery of the baby and placenta. No medicine reverses established disease, and symptoms usually improve once the baby is born.
Other measures are supportive: they protect the mother while the pregnancy continues but do not remove the cause. Antihypertensives (drugs that lower blood pressure) protect the mother, mainly from stroke, and she is monitored closely. Magnesium sulfate is given to prevent seizures (eclampsia) in severe pre-eclampsia. Low-dose aspirin is different again: it is preventive, offered to women at higher risk, and does not treat established disease.
The timing of birth is a judgement. It balances the risk to the mother of continuing the pregnancy against the risk to the baby of being born early, and it is sometimes safer for the baby to be born before 37 weeks. Delivery does not end the care, because the condition can persist or first appear after the birth, so monitoring continues.
Key facts
- Cause
- a poorly functioning placenta releases factors that injure the lining of the mother's blood vessels (endothelial dysfunction).
- Definitive step
- the baby and placenta are delivered, and the timing depends on gestation (the weeks of pregnancy) and the condition of mother and baby, because earlier birth is sometimes safer but delivering early carries its own risks for the baby.
- While waiting
- antihypertensives lower blood pressure and the risk of stroke, and the mother is monitored.
- Seizure prevention
- magnesium sulfate is the standard for preventing eclampsia in severe disease.
- Prevention
- low-dose aspirin is offered to women at higher risk to lower the chance of pre-eclampsia developing, and it does not resolve established disease.
- After birth
- pre-eclampsia can persist or first appear after delivery, so monitoring continues.
Exam traps
- Long-term blood pressure drugs alone do not resolve pre-eclampsia, because they lower blood pressure and the risk of stroke but treat a sign rather than the cause.
- Low-dose aspirin does not reverse pre-eclampsia that has already developed, because it is a preventive measure for women at higher risk and not a treatment once the condition is established.
- Magnesium sulfate does not treat the placental cause, because it is given to prevent seizures (eclampsia) in severe pre-eclampsia and is not enough on its own.
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