Table 1.

Stepwise sequential screening following first trimester combined screen

Group	N	No SS screening	Follow-up SS screening	P
Undecided	1,926 (72.9 %)	1,639 (85.1 %)	287 (14.9 %)	<0.0001
Yes	434 (16.4 %)	190 (43.8 %)	244 (56.2 %)
No	283 (10.7 %)	279 (98.6 %)	4 (1.4 %)
	2,643 (100 %)	2,108 (79.8 %)	535 (20.2 %)
			U vs Y	<0.0001
			U vs N	<0.0001
			Y vs N	<0.0001