Table 2: Demographics and summary of laboratory testing in two cases with false negative NIPT.

Case;
age (status)
BMIMedication, alcohol, and drugs1st trimester combined screening (NT)Blood for NIPT drawn at GA1Result of NIPT issued by a third partyPregnancy outcome; cytogenetic follow-up
Fetal fractionTri-13Tri-18Tri-21

Case  1
35 yrs
(G1P0)
22.0Negative1 : 190 risk for trisomy-18 (NT 1.6 mm)13 5/78.8% <1/10,000<1/10,000<1/10,000Amniocentesis at 21 weeks showed a nonmosaic 47, XY, +13 karyotype; sampling of placenta (9 biopsies) gave no evidence for the presence of euploid cells

Case  2
40 yrs
(G2P1)
22.4NegativeNot performed11 0/710.7%<1/10,000<1/10,000<1/10,000Amniocentesis at 20 weeks showed a nonmosaic 47, XX, +18 karyotype; sampling of placenta (10 biopsies) showed that a maximum of 20–30% euploid cells may have been present in the cytotrophoblast

Note. 1GA: gestational age.