From the Guidelines
The best way to diagnose preeclampsia is through a combination of blood pressure measurements and laboratory tests, with a focus on proteinuria assessment using a spot urine protein/creatinine ratio of ≥0.3 or a 24-hour urinary protein ≥300 mg per day. Preeclampsia is diagnosed when a pregnant woman has new-onset hypertension (blood pressure ≥140/90 mmHg) after 20 weeks of gestation, along with either proteinuria or evidence of end-organ damage 1. Essential laboratory tests include a complete blood count, comprehensive metabolic panel (focusing on liver enzymes, creatinine, and uric acid), and urinalysis for protein.
Key Diagnostic Criteria
- New-onset hypertension (blood pressure ≥140/90 mmHg) after 20 weeks of gestation
- Proteinuria (≥300 mg in a 24-hour urine collection or protein/creatinine ratio ≥0.3)
- Evidence of end-organ damage, such as:
- Thrombocytopenia (platelet count <100,000/μL)
- Elevated liver enzymes (twice the normal concentration)
- Renal insufficiency (serum creatinine >1.1 mg/dL)
- Pulmonary edema
- New-onset cerebral or visual disturbances In the absence of proteinuria, preeclampsia can still be diagnosed if there are signs of end-organ damage 1. Regular prenatal visits are crucial for early detection, as preeclampsia can develop rapidly. The diagnosis requires clinical vigilance because symptoms like headache, visual changes, or right upper quadrant pain may indicate severe preeclampsia requiring immediate medical attention 1.
Laboratory Tests
- Complete blood count
- Comprehensive metabolic panel (focusing on liver enzymes, creatinine, and uric acid)
- Urinalysis for protein Early diagnosis is critical as preeclampsia can progress to eclampsia (seizures) or HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), both of which carry significant maternal and fetal risks.
From the FDA Drug Label
Magnesium is said to have a depressant effect on the central nervous system (CNS), but it does not adversely affect the woman, fetus or neonate when used as directed in eclampsia or pre-eclampsia.
The FDA drug label does not answer the question.
From the Research
Diagnosis of Preeclampsia
The diagnosis of preeclampsia can be challenging, but several signs and measures can help distinguish it from other hypertensive disorders of pregnancy. Some of the key factors to consider include:
- Presentation during late gestation in a nullipara with edema and proteinuria 2
- Presence of one or more of the following: hemoconcentration, hypoalbuminemia, liver function and/or coagulation abnormalities, and increased urate levels 2
- Decreased antithrombin III levels, increments in serum iron and carboxyhemoglobin, and decreases in urinary calcium may also be useful in differentiating preeclampsia from less dangerous forms of hypertension 2
Role of Proteinuria in Diagnosis
Proteinuria is a key component of the diagnosis of preeclampsia, but recent guidelines suggest that it is not necessary for diagnosis 3, 4. The spot urinary protein to creatinine ratio (PCR) can be used as a "rule-out" test for proteinuria, with a threshold of 30mg/mmol 5. However, the 24-hour urine collection is still considered the gold standard test for quantitative diagnosis of proteinuria 5, 4.
Other Diagnostic Criteria
Other diagnostic criteria for preeclampsia include:
- Systolic blood pressure, which has been shown to be as important as diastolic blood pressure in the diagnosis of preeclampsia 3
- Symptoms of cerebral involvement, such as headache and visual changes, or signs of end-organ involvement, including abnormal laboratory tests (elevated serum creatinine or liver function tests, low platelet count) 3
- A combination of a high maximum diastolic pressure with a large increase from baseline can also be used to identify pre-eclamptic features 6
Limitations and Challenges
The diagnosis of preeclampsia can be challenging, and there are limitations and challenges to consider, including: