Methods	Central telephone randomisation.
Participants	Women aged 35 years or over with risk factors including Down’s syndrome in the family, a previous child with chromosomal abnormality, a parent who is a carrier of chromosomal abnormalities, history of a diseased or dead offspring, recurrent miscarriage, environmental exposure during pregnancy or anxiety. All women had a singleton pregnancy and gestational age confirmed by ultrasound. Exclusion criteria: high risk of genetic disease (25% or more), malformation suspected on ultrasound, intrauterine device, uterine haematomas and malformations 579 women were assigned to CVS, 581 women to EA and 114/1274 (9%) were excluded
Interventions	Transabdominal CVS was performed between 10 and 12 weeks with ultrasound guidance and a needle guide. The double needle technique was used (guide needle of 1.2 mm (18 G) and aspiration needle of 0.8 mm (21 G). Amniocentesis was done between 11 and 13 weeks with a needle guide and a 0.9 mm (20 G) standard AC needle. The filter system was used which allowed circulation of amniotic fluid (25 ml) back to the sac during sampling
Outcomes	Technical difficulties, abnormal karyotype, pregnancy complications, perinatal loss, neonatal complications
Notes	Trial was stopped early due to slow recruitment and due to clustering of talipes equinovarus in the EA group
Risk of bias
Item	Authors’ judgement	Description
Allocation concealment?	Yes	A - Adequate