Understanding Antenatal Screening and Diagnostic Tests

Antenatal screening and diagnostic test provide important insights into your baby’s health during pregnancy. They help identify potential genetic conditions, chromosomal abnormalities, and other health concerns early on. Understanding the differences between screening and diagnostic tests allows you to make informed decisions about your pregnancy care. Dr. Basu offers guidance to help you navigate these options with confidence.

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What’s the Difference Between Antenatal Screening and Diagnostic Tests?

Antenatal Screening Tests

Screening tests assess the likelihood of certain conditions but do not provide a definitive diagnosis. If a screening indicates a higher risk, further diagnostics may be recommended.

Antenatal Diagnostic Tests

Diagnostic tests provide a more conclusive result and can confirm whether a baby has a specific condition. They are typically offered when there is a higher risk based on screening tests, medical history, or ultrasound findings.

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Common Antenatal Screening Tests

1. Non-Invasive Antenatal Testing (NIPT) – From 10 Weeks

• A blood test that analyses fetal DNA in the mother’s blood.
• Screens for common chromosomal conditions such as Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13) as well as checking for an abnormal number of the sex chromosomes
• Highly accurate but not a diagnostic test.
• An early anatomy ultrasound is recommended between 11-13 weeks in conjunction with the NIPT

2.  Combined First Trimester Antenatal Screening (CFTS) – 11–14 Weeks

• Involves a maternal blood test and an ultrasound (nuchal translucency scan).
• Assesses the risk of chromosomal abnormalities like Down syndrome.
• Less accurate than NIPT

3. Second Trimester Screening  – 14–20 Weeks

• A blood test that measures specific hormones to estimate the risk of chromosomal abnormalities.
• Often used when FTCS or NIPT has not been performed.

4. Ultrasound Scans (Multiple Stages)

• Dating Scan (6–12 weeks): Confirms pregnancy and estimates due date.
• Nuchal Translucency Scan/ Early Anatomy Scan (11–13 weeks): Assesses chromosomal risk.
• Morphology Scan (18–22 weeks): Examines fetal development and detects structural abnormalities.

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Common Antenatal Diagnostic Tests

1. Chorionic Villus Sampling (CVS) – 11–14 Weeks

• A small sample of placental tissue is collected via the abdomen or cervix.
• Tests for genetic and chromosomal conditions.
• Small risk of miscarriage 

2. Amniocentesis – 15–20 Weeks

• A small amount of amniotic fluid is withdrawn and tested for chromosomal and genetic conditions.
• Provides a definitive diagnosis for conditions like Down syndrome.
• Small risk of miscarriage 

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Which Test Is Right for You?

Choosing the right antenatal tests depends on factors such as age, family history, and personal preferences. Some women opt for screening only, while others may choose diagnostic tests for a clearer result. Dr. Basu provides personalised guidance to help you make the best decision for your pregnancy.

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Supporting You Through Your Pregnancy Journey

Understanding antenatal testing can feel overwhelming, but you don’t have to navigate it alone. Dr. Basu ensures you have the information and support you need to make informed choices about your baby’s health.

Book a consultation today to discuss your antenatal testing options with a trusted obstetrician.