Table 1.

Demographic characteristics of the reference and test samples.

Characteristic	Reference Set (n = 1698)	Test Set (n = 109)
GA at NIPT (weeks)
First trimester (6–13)	1594	89
Second trimester (14–27)	104	20
Maternal age (years)
20–29	54	3
30–39	1314	79
≥40	330	27
Advanced maternal age (≥35 years)	1291	85
BMI
<18.5	140	12
18.5–25	1293	81
25–30	213	9
≥30	52	7
Pregnancy
Singleton	1623	105
Twin	75	4
Secondary outcomes
Trisomy 18		5
Trisomy 21		33

GA: gestational age.