Antenatal Screening

• Methods of Antenatal Screening

  • Ultrasound imaging

  • Blood and urine tests

  • Diagnostic testing
• Ultrasound Imaging

  Pregnant women are normally offered 2 ultrasound scans

  1.A dating scan takes place between 8 and 14 weeks. This gives information about the stage of gestation and the due date along with

  tests for marker chemicals which vary normally during pregnancy.

  2.Anomaly scans take a close look at the foetus and the uterus. These

  take place between 18 and 20 weeks. Anomaly scans may detect

  serious physical abnormalities in the fetus.
• Blood and Urine Tests

  
  

  • Routine blood and urine tests are carried out throughout pregnancy to monitor the concentrations of marker chemicals.

  
  

  • Measuring a chemical at the wrong time

  could lead to a false positive result.

  
  

  • An atypical chemical concentration can

  lead to diagnostic testing to determine if

  the foetus has a medical condition.
• Diagnostic Testing

  • Diagnostic testing produces results that establish whether a person has a specific condition or disorder.

  • Here we will look at two diagnostic tests:

  – Amniocentesis

  – Chorionic villus sampling (CVS)

  • There are some advantages and disadvantages of both types of test.
• Under what circumstances are further diagnostic tests carried out ?

  • As a result of a potential problem resulting from routine screening.

  • For individuals in high risk categories ( e.g women over 35)

  • Where there is a family history of a harmful genetic disorder.

  
  

  • In deciding to proceed with these tests, the element of risk associated with the tests is assessed.

  
  

  • the decisions the individuals concerned are likely to make if a test is positive are also considered.
• Diagnostic Tests Amniocentesis

  • amniocentesis – withdrawal of a little amniotic fluid containing fetal cells

  – Carried out about 14-16 weeks of pregnancy

  – Cells are cultured, stained and arranged to show the full chromosome compliment arranged as homologous pairs. This is called a karyotype.
• CVS (chorionic villus sampling)

  • Involves taking a small sample of placental cells.

  • Carried out as early as 8 weeks into pregnancy

  • Carries a higher risk of miscarriage than amniocentesis.

  • Cells from samples can be cultured to obtain a karyotype to diagnose a range of conditions.
• In deciding to proceed with diagnostic tests, the element of risk will be

  assessed, as will the decisions the individuals concerned are likely to make if a test is positive.
• Anomaly scans take a close look at the foetus and the uterus. These take place between 18 and 20 weeks. Anomaly scans may detect serious physical abnormalities in the fetus.
• A dating scan takes place between 8 and 14 weeks. This gives information about the stage of gestation and the due date along with tests for marker chemicals which vary normally during pregnancy.