A new contingent screening strategy increased detection rate of trisomy 21 in the first trimester

Table 2 Characteristics of biomakers of singleton pregnancies affected by trisomy 21 and unaffected pregnancies

Characteristic	Serum biochemical screening			Combined first-trimester screening
	Unaffected	Trisomy 21	P	Unaffected	Trisomy 21	P
Number	35,261	47		35,979	47
Serum free β-hCG (MoM)	0.99(0.67 ~ 1.52)	2.14(1.21 ~ 2.93)	< 0.01	0.99(0.67 ~ 1.52)	2.31(1.23 ~ 2.94)	< 0.01
Serum PAPP-A (MoM)	1.02(0.71 ~ 1.43)	0.42(0.25 ~ 0.60)	< 0.01	1.02(0.71 ~ 1.43)	0.42(0.26 ~ 0.62)	< 0.01

Data are given as median (interquartile range) or n (%). β-hCG, beta-human chorionic gonadotropin, PAPP-A, pregnancy-associated plasma protein-A. MoM,multiples of the median

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