The maternal serum screen is an aneuploidy screening test which is only available during the first trimester period whereas NIPT can be offered anytime during a pregnancy. The accuracy of serum screening is not as high as NIPT for the common aneuploidies and it has both a higher false positive and a higher false negative rate than NIPT. This means serum screening incorrectly reports that your baby has a high risk of a genetic change when they do not, or a low risk of a genetic change when the baby may actually have a genetic abnormality, at higher rates than with the NIPT test.