Screening Tests

 A mother’s joy begins when new life is stirring inside… when a tiny heartbeat is heard for the very first time, and a playful kick reminds her that she is never alone.” – Unknown


Screening tests help us check that everything is progressing normally and that both you and baby are healthy.  Here is an explanation of the routine tests you will have during your pregnancy.


(Combined first trimester screening)

This consists of a maternal blood test taken from 10 weeks gestation and a fetal ultrasound for nuchal translucency done at 12-13 weeks gestation.  The results are put into a mathematical calculation along with other factors such as maternal age and you receive a risk assessment of the likelihood of your baby having a chromosomal abnormality - particularly Down's syndrome risk.  The test is only a risk assessment so there are false positives (when you screen high risk but your baby is healthy), and false negatives (when you screen low risk but your baby has Down's syndrome).   Overall the test picks up about 85% of babies with Down's syndrome.   Currently, the Ministry of Health funds the combined maternal serum test. 


The nuchal translucency scan measures the thickness of the black space (fluid) in the neck area of the foetus.  In most pregnancies some fluid can be seen however if there is more than the normal amount of fluid, then the risk of chromosomal abnormality is increased.  There are some other implications of increased fluid which will be explained if relevant.


This is a highly accurate maternal blood test for identifying pregnancies at increased risk of chromosome conditions such as Down's syndrome.  It detects >99% of Down's syndrome pregnancies and is available privately from 10 weeks of pregnancy.  Illumiscreen is currently available for around $500.00.


Amniocentesis is usually performed at 15+ weeks gestation and is an invasive diagnostic test where a sample of the amniotic fluid (water surrounding he baby) is withdrawn using ultrasound guidance and the foetal cells in the fluid examined for chromosome abnormalities.


The anatomy scan is between 18-20 weeks gestation and will look at how the baby is developing.  A systematic examination of the baby looks closely at all limbs, organs such as the heart, brain and kidneys, to check for abnormalities. It also looks at the location of the placenta in the uterus. It may be possible to tell the sex of the baby if all limbs are in a suitable position.