Methods	3-way randomisation of low-risk women (TA vs TC vs AC). A 2-way randomisation of high-risk women (TA vs TC). Central randomisation (unknown) with stratification for genetic risk
Participants	2 centres in Denmark from 1985-1990. Eligible low-risk women: age > 34 or father > 49, history of or anxiety about chromosomal abnormality, > 3 spontaneous miscarriages with viable fetus at 9-11 weeks. Eligible high-risk women: history of translocation, late termination or fetus at risk of metabolic disorder with a viable fetus at 9-11 weeks. Exclusions: active bleeding, intrauterine device, genital infection, severe mental illness, use of teratogenic drugs, history of neural tube defects and discrepant dating
Interventions	CVS vs second trimester AC. TA CVS vs second trimester AC. TC CVS vs second trimester AC. TC CVS vs TA CVS.
Outcomes	Pregnancy outcome, antenatal complications and diagnostic accuracy
Notes
Risk of bias
Item	Authors’ judgement	Description
Allocation concealment?	Yes	A - Adequate