genetics and prenatal diagnosis
Last reviewed 01/2018
The main indication for chromosome analysis is a pregnancy that has been identified as being at risk of a cytogenetic disorder due to:
- following a high risk screening result for Down's syndrome
- abnormalities found on ultrasound scan
- a previous chromosome abnormality
- where a parent is known to carry a chromosome abnormality
- advanced maternal age
Genetic studies on the foetus can be undertaken on amniotic fluid cultures (usually at about 15-16 weeks gestation), by chorionic villus sampling (CVS) (from 11 weeks gestation), or by foetal blood sampling (from 18 weeks gestation). Foetal urine and pleural effusions are also occasionally used.
Down's screening (part of the Fetal Anomaly Screening Programme)