The double marker test, also known as the dual marker test, is a maternal blood screening conducted during the first trimester of pregnancy. This test measures the levels of beta-human Chorionic Gonadotropin (β-hCG), a pregnancy hormone, and Pregnancy-Associated Plasma Protein-A (PAPP-A) in the mother's blood.
Healthcare providers recommend this test, particularly for women over the age of 35, as they have a higher risk of giving birth to a baby with chromosomal abnormalities such as Down's syndrome. The double marker test is often performed alongside the nuchal translucency (NT) scan to confirm the presence of any genetic anomalies.
• Advantages
• Preparation
• When It's Recommended
• Uses
• How It's Performed
• Interpreting Results
• Normal Range
• Cost
• Double Marker vs. Triple Marker Test
• Detection of Trisomy 13: Helps identify trisomy of chromosome 13, which can cause severe birth defects and intellectual disabilities in the infant.
• Detection of Down's Syndrome: Assists in detecting chromosomal abnormalities of chromosome 21, leading to Down's syndrome.
• Assessment of High-Risk Factors: Evaluates potential risks during pregnancy that could be harmful to both the mother and the developing fetus.
• High Detection Rates: Offers reliable detection rates for certain chromosomal abnormalities.
• Informed Decision-Making: A positive result allows couples to consider further diagnostic tests for confirmation or to discuss available options with their healthcare provider.
The test requires a blood sample from the mother and may include an ultrasound scan. Prior to the test:
• Ensure all equipment and machines are properly sterilized and prepared.
• Gather maternal health details such as in vitro fertilization reports, body weight, and diabetic status.
The double marker test is ideal for pregnant women over the age of 35. It is also recommended if there are indications of genetic abnormalities, which can be determined by reviewing the family's medical history or pedigree chart.
• Detecting Down's Syndrome: Identifies the risk of Down's syndrome in the unborn child.
• Assessing Physical Abnormalities: Detects potential issues such as loss of muscle mass, short neck, or excess skin growth at the back of the infant's neck.
• Ensuring Maternal and Fetal Well-being: Evaluates risks of physical features like upward slanting eyes, stunted growth, flattened facial appearance, and severe mental and physical handicaps in newborns.
• Detecting Trisomy 18: Identifies trisomy of chromosome 18, which can lead to clenched fists and deformities of vital organs like the heart, lungs, stomach, and intestines.
• Identifying 'Rocker Bottom Feet': Detects foot deformities where the feet resemble the bottom of a rocking chair.
• Detecting Other Abnormalities: Identifies conditions such as microcephaly (small head), micrognathia (abnormally shaped jaws and mouth), clenched fists, arched spine, and abnormal chest shape.
• Assessing Neurological Development: Detects short sternum and delays in neurological functions of the brain.
• Identifying Umbilical Hernia: Helps distinguish umbilical hernia in the mother during pregnancy.
The test involves a simple blood draw from the pregnant woman. The steps include:
1. Blood Sample Collection: A healthcare professional uses a syringe to draw blood from a vein.
2. Preparation: An elastic band is tied around the upper arm to make the veins more prominent.
3. Cleaning the Site: The area is cleaned with an antiseptic to prevent infection.
4. Needle Insertion: A needle is gently inserted into the vein to collect the blood sample.
5. Sample Preservation: The blood sample is preserved for laboratory testing.
Note: The test poses minimal risks. In rare cases, there may be slight bleeding, formation of a hematoma, bruising, or infection at the needle insertion site.
Results are categorized as either screen positive or screen negative and are presented in the form of ratios. Interpretation depends on:
• The mother's age
• The gestational age of the fetus
• Ultrasound findings during the gestation period
Screen Positive Results:
• Ratios from 1:10 to 1:250 indicate a higher risk of chromosomal abnormalities.
• For example, a ratio of 1:10 means there is a 1 in 10 chance of the fetus developing a genetic disorder, which is significant.
Screen Negative Results:
• Ratios of 1:1000 or higher suggest a lower risk.
• A ratio of 1:1000 indicates a much lower chance of genetic disorders.
If the test results are positive, the doctor may recommend further diagnostic procedures like amniocentesis for confirmation. Couples can then discuss their options with their healthcare provider, considering the potential risks and making informed decisions about the pregnancy.
See how we combine technology and compassion in our care
