Down’s syndrome/Fragile X (FXS)/Spinal muscular atrophy (SMA)/Cystic fibrosis (CF)/Alef8

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Screening estimates the risk of having a disorder.  Those found to be at high risk have a number of choices, depending on the circumstances.  With antenatal screening, the main choice is to have an invasive diagnostic procedure such as amniocentesis and chorionic villus sampling (CVS) which can cause a miscarriage.

Prenatal diagnosis establishes whether or not a disorder is definitely present in the fetus. Antenatal screening, on the other hand, estimates the risk of having the disorder. Screening is not intended to replace diagnosis, rather it aims to provide information to help decide whether prenatal diagnosis is warranted.

Such risk estimation is important since, for most disorders, prenatal diagnosis is only possible by an invasive procedure which can cause a miscarriage. The main procedures are amniocentesis and chorionic villus sampling (CVS). Chromosomal anomalies and monogenetic disorders require an invasive procedure but for some structural abnormalities prenatal diagnosis can be achieved by specialist ultrasound.

Those considering screening need to make a number of decisions. Initially there are three: whether to be screened at all, for which specific disorders, and which test. For those screened and identified as high risk, there is the further decision whether to undergo prenatal diagnosis. Following this, if the pregnancy is found to be affected, a further decision will need to be made: whether or not to have a termination of pregnancy.