Before the technology behind NIPS was developed, the most common way of non-invasively assessing the risk for a chromosome condition in a pregnancy was a method called serum screening. This screening method relies on measuring proteins in the mother’s blood combined with measurements taken during a specialized ultrasound to determine the risk of the pregnancy being affected.
NIPS is a newer technology that, like serum screening, uses a blood sample from the mother. But instead of looking at proteins and ultrasound measurements, NIPS analyzes DNA from the baby’s placenta that is floating around in the mother’s blood.
NIPS is more sensitive than serum screening. This means there is less chance of getting a negative result when in fact the baby really does have a chromosome condition. NIPS is also more specific than serum screening. This means there is less chance of getting a positive result when in fact the baby does NOT have a chromosome condition. This is important because false positives can lead to unnecessary invasive diagnostic procedures.
Regardless of whether you pursue serum screening or NIPS, remember that only a diagnostic test — chorionic villus sampling (CVS) or amniocentesis — can provide a definitive answer as to whether a pregnancy is affected with a chromosome condition. These procedures are invasive and pose small risks, including miscarriage, so often women will wait to do CVS or amniocentesis until after they’ve been identified as having increased risk through a screening test.