What is OSCAR test?

The test is designed to screen for the following 3 groups of problems in pregnancy:

1. Risks of common chromosomal abnormalities (including Down Syndrome, Edward Syndrome and Patau Syndrome) using the Fetal Medicine Foundation (FMF, London) software.
2. Early structural abnormalities such as anencephaly (absence of skull), exomphalos (protrusion of intestines through an abdominal wall defect), megacystis (enlarged bladder), etc.
3. Risk of severe pre-eclampsia (i.e a serious condition during pregnancy charactised by high blood pressure with proteins in the urine) occurring before 34 weeks and intrauterine growth restriction (i.e. reduced growth of the fetus)

These risks are calculated through integration of the following data:

Historical data such as:

• Mother's age, height and weight
• History of chronic high blood pressure or pre-eclampsia
• Type of pregnancy - natural or In-Vitro fertilisation
• Smoking status

High resolution ultrasound findings of:

• Crown rump length (CRL)
• Nuchal Transluscency (NT) which is increased in majrity of fetuses with chromosomal abnormalities
• Fetal heart rate
• Obvious early structural abnormalities
• Uterine artery doppler

Mother's blood for 2 biochemical markers (i.e. PAPP-A, free beta hCG)

One additional marker (i.e nasal bone,ductus venosus, tricuspid regurgutation or facial angle) may be useful in assessing the risk of those with borderline risks.

When the calculated risk of chromosomal abnormalities exceeds a threshold level set at 1:300, invasion diagnostic procedures such as chorionic villus sampling or amniocentesis may be advised to check the chromosomes of the unborn baby. This strategy allows detection of 90% of Down Syndromes (i.e 10% of DS will not be detected)