The NIPT test estimates the risk of a fetus having Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18) and Patau syndrome (Trisomy 13). Trisomies occur when three, instead of the usual two, copies of a chromosome are present. Edwards and Patau syndromes are much rarer than Down but are very serious and many affected babies do not survive. If fetal sex determination is requested, the accuracy is greater than 99%. In rare cases a “sex determination failure” result may be reported if there is insufficient data to support the sex determination analysis. A “sex determination failure“ does not impact the trisomy result.