TABLE 1.

Details of false negative cases and pregnancy results.

Case	MA	BMI	GW	PA	Twin pregnancies	IVF-ET pregnancies	Ultrasound results
Case 1	26	16.26	18 + 3	28	NO	NO	Nasal insufficiency, left renal sinus splitting
Case 2	33	19.84	16 + 4	35	NO	NO	N/A
Case 3	31	26.57	17 + 3	39	NO	NO	Multiple malformations
Case 4	30	23.15	26 + 4	31	NO	NO	Hypoplastic nasal bone
Case 5	26	17.97	18 + 4	27	NO	NO	Absent nasal bone
Case 6	36	21.29	16 + 1	36	NO	NO	Absent nasal bone
Case 7	28	25.91	18 + 4	29	NO	NO	Multiple malformations: small jaw, cystic dilatation, overlapping fingers on the left hand
Case 8	24	23.05	20 + 4	24	NO	NO	Right ventricular outflow tract and pulmonary stenosis
Case 9	41	26.50	16 + 5	45	YES	YES	Normal left fetus, right fetus with a complex malformation

BMI, body mass index; GW, gestational age at blood collection; IVF-ET, in vitro fertilization-embryo transfer; MA, maternal age; PA, paternal age.