Preeclampsia is a serious pregnancy complication characterized by high blood pressure, typically developing after 20 weeks of gestation or even postpartum. This condition can lead to significant risks for both the mother and the developing baby, including impaired organ function, seizures, or fluid in the lungs. Early and accurate detection through various tests is important to manage preeclampsia and improve outcomes.
Initial Screening and Diagnosis
Routine prenatal visits are important for the initial screening for preeclampsia. During these appointments, healthcare providers monitor blood pressure.
Alongside blood pressure checks, a urine dipstick test for protein is a common screening tool. This test uses a chemically treated strip that changes color if protein is present in the urine. While a positive dipstick result suggests the need for further investigation, the amount of protein detected by this method does not indicate the severity of preeclampsia.
These initial indicators, high blood pressure and the presence of protein in urine, are the first signs that prompt healthcare providers to conduct more comprehensive evaluations. Timely identification during routine check-ups allows for closer monitoring and further testing.
Further Laboratory Evaluations
If initial screenings raise concerns, healthcare providers will conduct more specific laboratory tests to assess preeclampsia’s impact on the body. Blood tests are performed to check liver function, with elevated levels of enzymes like aspartate aminotransferase (AST) and alanine aminotransferase (ALT) indicating liver damage.
Kidney function is assessed through blood tests that measure creatinine and blood urea nitrogen (BUN) levels. An elevated serum creatinine level, typically above 1.1 mg/dL, or a doubling of the creatinine concentration, indicates impaired kidney function. A complete blood count (CBC) is also performed to check platelet levels; a low platelet count, generally below 100,000/mm³, is a sign of preeclampsia.
For a more definitive assessment of protein in the urine, a 24-hour urine collection test is ordered. This test provides a precise measurement of the total protein excreted over a full day, with 300 mg or more indicating proteinuria. While a dipstick test offers a quick screen, the 24-hour collection offers a more accurate measure of kidney involvement. Alternatively, a spot protein-to-creatinine ratio of 0.3 or higher is also used as an indicator.
Monitoring Fetal Health
When preeclampsia is suspected or diagnosed, monitoring the baby’s well-being becomes an aspect of care. Ultrasound scans are performed to assess fetal growth, as preeclampsia can restrict blood flow to the placenta, leading to slower growth. These scans also measure amniotic fluid levels, which can be affected by the mother’s condition.
Doppler studies, a specific type of ultrasound, are used to evaluate blood flow through the umbilical and middle cerebral arteries. These studies provide information on how well the baby is receiving blood and oxygen, helping to detect changes in blood flow that indicate fetal compromise. Doppler changes can often be detected earlier than other signs of fetal distress.
Other fetal surveillance methods include non-stress tests (NSTs), which monitor the baby’s heart rate in response to movement. A normal NST shows an increase in fetal heart rate with activity, indicating adequate oxygenation. If the NST results are not normal, it may suggest the baby is not receiving enough oxygen, potentially prompting further testing or intervention.
Interpreting Diagnostic Findings
Healthcare providers synthesize the results from various tests to arrive at a definitive preeclampsia diagnosis. The diagnosis typically involves new-onset hypertension after 20 weeks of gestation, defined as a systolic blood pressure of 140 mmHg or higher, or a diastolic blood pressure of 90 mmHg or higher, on two occasions at least four hours apart.
In addition to elevated blood pressure, the diagnosis often includes signs of organ dysfunction. This can be indicated by proteinuria, such as 300 mg or more of protein in a 24-hour urine collection, or a protein-to-creatinine ratio of 0.3 or higher. Other findings include decreased platelet count, elevated liver enzymes, fluid in the lungs, or new-onset headaches or visual disturbances.
Preeclampsia can be classified as mild or severe based on the constellation of symptoms and test results. Severe preeclampsia may involve blood pressure readings of 160/110 mmHg or higher, significant proteinuria (e.g., 5 grams or more in 24 hours), or more pronounced signs of organ damage such as low platelet counts or elevated liver enzymes. The diagnosis of preeclampsia is a comprehensive clinical decision, relying on a combination of these signs, symptoms, and laboratory findings rather than any single test result.