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   Prenatal Genetic Screening
   Non-Invasive Screening for Chromosome Abnormalities
   Screening based on Ultrasound
   Screening Based on 1st Trimester Serum
   First Trimester Screening
   Multiple Pregnancy
   Invasive Testing
   Training Centre
   References and Resource
   Registered NT Centres

Prenatal genetic screening is a rapidly changing field. This website provides information about prenatal screening and diagnosis for health care providers. It is standard of care to offer genetic counseling and the option of invasive testing where indicated, to all couples with one or more of these indications.

Table 1

Indications for Prenatal Genetic Testing
  • Late maternal age (>35 years at delivery)
  • Previous trisomic offspring (increases baseline by 0.75%)
  • Parental translocation carrier
  • Family/personal history of genetic disorder or birth defect
  • Positive screening test (Ultrasound and/ or biochemistry)

The majority of birth defects and chromosome abnormalities occur among otherwise low risk couples:

• Approximately 1:160 live born infants have a chromosome abnormality.
• Over 80% of Down syndrome infants are born to women under 35 years of age.
• All couples have a 2-3 % risk of having a child with a birth defect.

If prenatal diagnosis were restricted to high risk groups (Table 1), the majority of abnormalities would go undetected.

Thus, a major focus of prenatal diagnosis in recent years has been to develop effective non-invasive screening tools applicable to the entire pregnant population.