The triple test assesses the risk of having a Down's baby based on:

• maternal age
• maternal serum markers - alpha feta protein, unconjugated oestriol and total human chorionic gonadotrophin.

Serum is taken from 15-20 weeks gestation, ideally 16 weeks. A high hCG, low AFP and low oestriol suggest a Down's child. Results are expressed in terms of the risk of having a Down's child eg. 1 / 145. Detection rates range from 45-65% with a 5% false positive rate. Those with a risk greater than 1 in 200 are offered amniocentesis.

Other risks may also be detected eg. a high AFP suggests a neural tube defect.

Improved combined methods of screening are now available and women should not be offered the triple test in the UK.

Note that the triple test was known as the Barts test in some areas.

The recommended method of screening for Down's syndrome is using the Combined Test. Combined screening can be carried out in the first trimester and up to 14 weeks and 1 day of pregnancy.

Women who present too late for combined screening should be offered quadruple testing in the second trimester of pregnancy.

For more information: NHS Fetal Anomaly Screening Programme (NHS FASP) www.fetalanomaly.screening.nhs.uk

References:

• 1. NICE. Antenatal care: routine care for the healthy pregnant woman. England: NHS National Institute for Health and Clinical Excellence; 2008 Mar. Report No.: Clinical guidelines CG62.
• 2. NHS Fetal Anomaly Screening Programme. Antenatal screening - working standards for Down's syndrome screening 2007. NHS FASP; 2007.
• 3. NHS Fetal Anomaly Screening Programme. Consent standards for screening fetal anomalies during pregnancy 2007. NHS FASP; 2007.
• 4. NHS Fetal Anomaly Screening Programme. Screening for Down's syndrome: UK NSC Policy recommendations 2011-2014 Model of Best Practice. Department of Health; 2011.
• 5. Kirwan D, NHS FASP. 18+0 to 20+6 weeks fetal anomaly scan -National standards and guidance for England 2010. Exeter, England: NHS Fetal Anomaly Screening Programme; 2010.