Positive Integrated Prenatal Screening (IPS): What It Means and Next Steps

What Is IPS?

Integrated Prenatal Screening combines:

First trimester (11–13+6 wks): Nuchal translucency (NT) ultrasound + PAPP-A blood test.
Second trimester (15–20+6 wks): Quad screen (AFP, hCG, uE3, inhibin A).
Maternal age, weight, ethnicity, diabetes status factored in.
Single report after second trimester with risk estimate for trisomy 21, 18, 13, and open neural tube defects (ONTD).

“Positive” = screen-positive = risk exceeds lab’s cut-off (e.g., 1:270 for T21).
Not a diagnosis. Most screen-positive fetuses are unaffected (false positive rate ~5%).
Positive predictive value (PPV) depends on prior risk: e.g., at 35, PPV for T21 ~1:20; at 25, ~1:100.

Genetic counseling – review result, discuss options, values.
Diagnostic testing (definitive):
- CVS (10–13 wks): Chorionic villus sampling – placental biopsy. 0.5–1% miscarriage risk. Karyotype + microarray.
- Amniocentesis (≥15 wks): Amniotic fluid culture. 0.1–0.3% miscarriage risk. Karyotype + microarray.
NIPT (cell-free DNA): High sensitivity/specificity for T21/18/13; not diagnostic. Can be intermediate step before invasive test.
Detailed anatomy ultrasound (18–22 wks): Assess structural markers (nasal bone, heart, etc.).

If diagnostic test normal → reassurance; continue routine care.
If abnormal → counseling on condition, prognosis, pregnancy management, termination options (per local law).
Support resources: genetic counselors, MFM specialists, support organizations (NDSS, SOFT).

A positive screen means increased probability, not certainty. You have time to gather information and make informed choices.