Table 1.

Comparison of two screening periods in Northern Finland.

PERIOD	N	T21 N	PREVALENCE TOTAL BIRTH	MEAN AGE	PROPORTION ≥35 Y %	DR %	FPR %	INVASIVE PROCEDURES	NIPN*
2002–06	16.749	53	1:316 1:1396	29.6	17.4	77.3	4.9	795	15
2007–11	31.147	83	1:375 1:1639	29.4	15.3	77.1	2.8	913	11

Note:

^*Number of invasive procedures needed to detect one case of Down’s syndrome.