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Maternal Serum Screening Tests

Maternal Serum Screening (MSS) is a prenatal blood test used to evaluate the risk of certain genetic conditions and birth defects in a developing baby. This test is non-invasive and involves analyzing specific substances in a pregnant woman’s blood.

A pregnant woman holding her belly, promoting the Maternal Serum Screening Test in Jaipur being conducted at Jaipur Molecular Lab for Double/Dual Marker Test for the 11th to 13.6th week of pregnancy. The test measures Free Beta hCG and PAPP-A levels to assess the risk incidence of Trisomy 21, 18, and 13.

Purpose of Maternal Serum Screening

This screening evaluates the likelihood of specific conditions, including:

  1. Chromosomal Abnormalities:
    • Down Syndrome (Trisomy 21).
    • Edwards Syndrome (Trisomy 18).
  2. Neural Tube Defects (NTDs):
    • Spina Bifida.
    • Anencephaly.

Types of Maternal Serum Screening

Maternal serum screening occurs during the first or second trimester and includes one or more of the following:

1. First-Trimester Screening

This test measures hCG (human chorionic gonadotropin) and PAPP-A (pregnancy-associated plasma protein A) in the blood. Additionally, ultrasound examines the baby’s nuchal translucency (fluid at the back of the neck). It takes place between 11 and 13.6 weeks of pregnancy.

2. Second-Trimester Screening (Quad Screen)

The quad screen measures four substances:

  1. AFP (Alpha-fetoprotein), produced by the baby.
  2. hCG, secreted by the placenta.
  3. Estriol, an estrogen made by the baby and placenta.
  4. Inhibin A, another hormone from the placenta.
    Doctors typically perform this test between 15 and 20 weeks of pregnancy.

3. Integrated Screening

By combining first- and second-trimester results, integrated screening offers a more accurate risk assessment.

How It Works

First, a blood sample is taken from the mother. Next, the lab measures specific substances in the sample. These results, along with the mother’s age, weight, and gestational age, help calculate the risk of certain conditions. Finally, a risk score is provided, guiding further testing if needed.

Advantages of Maternal Serum Screening

  1. Non-Invasive: Only a blood sample is required.
  2. Early Risk Assessment: Detects potential risks during the early stages of pregnancy.
  3. Guides Further Testing: Results indicate whether additional tests, such as NIPT or amniocentesis, are necessary.

Limitations

  1. Not Diagnostic: MSS estimates risk but doesn’t confirm conditions.
  2. Possible False Positives/Negatives: Some results might be inaccurate, leading to unnecessary follow-ups.
  3. Less Accurate than NIPT: While effective, MSS doesn’t match the precision of NIPT for detecting chromosomal abnormalities.

Who Should Consider This Test?

Although all pregnant women can undergo MSS, it is especially beneficial for:

  • Women aged 35 or older.
  • Those with a family history of genetic disorders.
  • Pregnancies achieved through assisted reproductive techniques like IVF.