ABSTRACT
This patient wants to know whether or not her baby is affected, which means you need to offer her a diagnostic rather than a screening test. She wishes to have a test as soon as possible; a chorionic villous sample (CVS) can be taken after 10 weeks’ gestation, whereas an amniocentesis is offered from 15 weeks onwards. An earlier CVS carries a risk of limb reduction defects, whereas an amniocentesis performed before 15 weeks has a higher risk of miscarriage.
