Pre-eclampsia is a complication that can occur during pregnancy and is characterized by high blood pressure and protein in the urine. It typically occurs in the second half of the pregnancy and has an incidence rate of around 2% in Hong Kong. Severe pre-eclampsia can be dangerous and potentially life-threatening.
Diagnosis of Pre-eclampsia
Diagnosis is made based on the following criteria:
- Elevated blood pressure: In women with previously normal blood pressure, blood pressure ≥140 mmHg systolic or ≥90 mmHg diastolic on 2 occasions taken at least 4-6 hours apart after 20 weeks’ gestation. In a woman with pre-existing hypertension before 20 weeks’ gestation, an increase in systolic blood pressure of ≥30 mmHg or an increase in diastolic blood pressure of ≥15 mmHg.
- Proteinuria: ≥ 0.3 grams (300 mg) of protein in a 24-hour urine sample or a spot urinary protein to creatinine ratio ≥0.3.
Risks for Mother and Baby
Pre-eclampsia can affect different systems of the pregnant woman and may lead to various complications, including:
- Eclampsia (generalized convulsion)
- Disruption of the clotting system
- Deterioration of kidney function
- Damage to the liver
- Risks of stroke, heart failure, and lung edema in severe cases
Pre-eclampsia also poses significant risks to the unborn child, including:
- Intrauterine fetal growth restriction
- Placental abruption
- Preterm delivery
- Intrauterine fetal death
Clinical Features of Pre-eclampsia
Most women with pre-eclampsia have no symptoms. Regular blood pressure measurement and urine tests for protein during antenatal check-ups are important. Women with significant protein in the urine may experience ankle swelling (ankle edema), although this symptom is not specific to pre-eclampsia and can also occur in normal pregnancies. Women with severe pre-eclampsia may experience symptoms such as headaches, blurred vision, stomach pain or pain on the right side of the abdomen, vomiting, low urine output, and hyper-reflexia.
Management of Pre-eclampsia
Delivery of the baby and the placenta is the only cure for pre-eclampsia. If pre-eclampsia occurs before 34 weeks of gestation, a balance must be made between the risks of continuing the pregnancy and the risks of preterm delivery for the baby. The main aims of management are to protect the mother from complications of severe pre-eclampsia, minimize the risk to the unborn baby, and deliver the baby when the risks of continuation of pregnancy outweigh the risks of prematurity.
Screening for Pre-eclampsia
Predictive factors for pre-eclampsia include various factors related to the pregnant woman and her family, such as the first pregnancy, older age and higher weight, chronic hypertension and kidney diseases, personal history of pre-eclampsia in previous pregnancies, and family history of pre-eclampsia. The use of mean arterial blood pressure (MAP) and ultrasound measurement of the uterine arteries in the first trimester between 11-13 weeks of gestation can also be useful for identifying women at high risk for pre-eclampsia. However, the majority of pregnancies with pre-eclampsia do not have any risk factors apart from being the first pregnancy.