CVS is usually done at 10 – 12 or 10 – 14 weeks, amniocenteses is usually done at 16 – 18 weeks. So many women who find out that they have a positive screen, or an increased risk for Down's ...
Of these women, 12 had persistently low levels on repeat. A total of 21 amniocenteses were done in this group. Three fetuses with trisomy 21 and one fetus with trisomy 18 were detected ...