Pre-eclampsia/preterm Screening

1. Pre-eclampsia: Overview

Pre-eclampsia is a pregnancy complication characterized by:

• High blood pressure (Hypertension): Defined as a blood pressure of 140/90 mmHg or higher after 20 weeks of gestation.
• Proteinuria: Excess protein in the urine, which is a sign of kidney dysfunction.
• Swelling (Edema) and headaches can also be common, though not always present.

In more severe cases, pre-eclampsia can develop into eclampsia, which involves seizures and can lead to organ failure or premature birth.

Risk Factors for Pre-eclampsia:

• First pregnancy
• Previous history of pre-eclampsia
• Age (under 20 or over 40)
• Multiple pregnancies (twins, triplets)
• Obesity or high BMI
• High blood pressure or kidney disease prior to pregnancy
• Family history of pre-eclampsia
• Gestational diabetes

2. Preterm Birth: Overview

Preterm birth is when a baby is born before 37 weeks of gestation, compared to the full-term gestation period of 37-42 weeks. Preterm birth is associated with an increased risk of neonatal morbidity and mortality.

• Very preterm: Born before 32 weeks.
• Moderate preterm: Born between 32 and 34 weeks.
• Late preterm: Born between 34 and 36 weeks.

Risk Factors for Preterm Birth:

• Previous preterm birth
• Multiple pregnancies (twins, triplets)
• Uterine or cervical abnormalities
• Infections or inflammation (e.g., urinary tract infections, periodontal disease)
• Chronic health conditions (e.g., diabetes, hypertension)
• Age (younger than 17 or older than 35)
• Smoking, alcohol use, or illicit drug use
• Stress or physical trauma

3. Screening for Pre-eclampsia

Early screening for pre-eclampsia can help in identifying women at higher risk so that preventive measures can be implemented. Traditionally, pre-eclampsia is diagnosed based on clinical signs, but newer screening methods aim to identify women at risk before symptoms develop.

Common Screening Methods for Pre-eclampsia:

1. Blood Pressure Monitoring:

• Regular blood pressure checks during prenatal visits are crucial to monitor for hypertension, which is the most common indicator of pre-eclampsia.
• Blood pressure should be checked at every prenatal visit starting from the first trimester to detect early signs of hypertension.

2. Urine Testing for Proteinuria:

• Urine tests to detect protein can be done during routine prenatal visits.
• Dipstick tests are typically used for initial screening.
• 24-hour urine collection or a urinary protein-to-creatinine ratio may be used to confirm significant proteinuria.

3. Screening Tests for Pre-eclampsia Risk (Blood Markers): Several biomarkers and blood tests have been identified to help screen for pre-eclampsia risk:

• Plasma Protein-A (PAPP-A) and Plasma Soluble Fms-Like Tyrosine Kinase (sFlt-1):
  • These biomarkers are tested in combination, as changes in their levels have been associated with pre-eclampsia risk.
  • sFlt-1 levels are elevated in women who develop pre-eclampsia, while PAPP-A levels are often lower.
  • A ratio of sFlt-1/PlGF (Placental Growth Factor) is also used to assess the likelihood of developing pre-eclampsia. Elevated sFlt-1 with low PlGF is a high-risk marker for pre-eclampsia.
• Mean Arterial Pressure (MAP) and Uterine Artery Doppler:
  • Uterine artery Doppler ultrasound measures blood flow in the uterine arteries and can help predict pre-eclampsia risk. Abnormal blood flow patterns (e.g., high resistance) can suggest a higher likelihood of developing pre-eclampsia.
• Aspirin Use:
  • Women identified as high-risk for pre-eclampsia (e.g., with previous pre-eclampsia, obesity, or multiple gestations) may be prescribed low-dose aspirin (81 mg daily) from the first trimester to reduce the risk of developing the condition.
• Serum Tests:
  • In some cases, blood tests for other markers, such as Endoglin and Angiopoietin-2, are also being studied for pre-eclampsia prediction.

Timing for Screening:

• Screening for pre-eclampsia risk typically occurs in the first trimester (especially for women at high risk) and again in the second trimester for regular monitoring. Aspirin may be started early if needed.

4. Screening for Preterm Birth

Preterm birth screening focuses on identifying women at risk for delivering prematurely, often before any clinical symptoms arise. The goal is to provide interventions that may help prevent or delay preterm labor and birth.

Common Screening Methods for Preterm Birth:

1. Cervical Length Measurement (Ultrasound):

• Cervical length measurement using transvaginal ultrasound is one of the most effective tools for screening for preterm birth risk.
• A shortened cervix (less than 25 mm before 24 weeks) is a significant risk factor for preterm birth.
• In women with a short cervix, a cerclage (cervical stitch) or progesterone therapy may be recommended to help prevent preterm labor.

2. Fetal Fibronectin (fFN) Test:

• The fetal fibronectin test is a test used to detect the presence of a protein called fetal fibronectin, which is produced by the fetal membranes and is typically found in the cervix in low amounts.
• If fFN levels are elevated, it can suggest that the cervix may be starting to dilate, which can increase the likelihood of preterm labor.
• The test is typically performed between 22-34 weeks of pregnancy and is often used when a woman has symptoms of preterm labor, such as contractions or vaginal discharge.
• A negative result (no fetal fibronectin detected) is highly reassuring and suggests that preterm birth is unlikely.

3. History of Preterm Birth:

• Women who have had a previous preterm birth are at higher risk of delivering prematurely again.
• These women are typically monitored more closely, and preventive measures like progesterone therapy or cervical cerclage may be used.

4. Blood Tests:

• Some emerging blood tests look for specific biomarkers that are associated with preterm labor. These include:
  • C-reactive protein (CRP): A marker for inflammation that may be elevated in women at risk for preterm birth.
  • Pro-Inflammatory Cytokines: Elevated levels of cytokines have been linked to preterm labor.

5. Lifestyle and Environmental Factors:

• Women who smoke, have high stress, or are exposed to environmental hazards may be at higher risk for preterm birth.
• Screening questionnaires that assess these lifestyle factors may help in determining a woman’s preterm birth risk.

5. Management and Prevention:

For high-risk women identified through screening for pre-eclampsia and preterm birth, there are several management strategies:

• Aspirin: For women at high risk of pre-eclampsia, low-dose aspirin is often prescribed.
• Progesterone: Progesterone supplementation (e.g., vaginal progesterone) is commonly given to women with a short cervix or a history of preterm birth to reduce the risk of preterm labor.
• Cervical Cerclage: In some cases, a cervical stitch (cerclage) may be placed to prevent the cervix from opening prematurely.
• Monitoring: Women at high risk for pre-eclampsia or preterm birth may be closely monitored with more frequent ultrasounds, blood pressure checks, and blood tests.

Summary:

Pre-eclampsia and preterm birth are serious pregnancy complications that can have significant maternal and fetal risks. Screening for these conditions typically involves:

• Blood tests to detect markers of risk (e.g., sFlt-1, PAPP-A, PlGF).
• Blood pressure monitoring to detect hypertension.
• Urine tests for protein to assess kidney function.
• Ultrasound to monitor cervical length and detect abnormal blood flow (for pre-eclampsia).
• Fetal fibronectin tests for preterm labor risk.

Early detection and appropriate interventions, such as aspirin therapy, progesterone, and cervical cerclage, can help reduce the risks associated with pre-eclampsia and preterm birth, improving outcomes for both the mother and the baby. Regular prenatal visits and screenings remain essential in ensuring the health of both mother and fetus throughout pregnancy.