What is the probability that my baby is healthy given I am 28 years old, have a 12‑week nuchal translucency of 2 mm, a visible nasal bone, a normal 16‑week anatomy scan, and a non‑informative NIPT result with zero positive predictive value and zero Z‑score?

Reassuring Prognosis: Very High Likelihood of a Healthy Baby

Given your young maternal age (28 years), normal nuchal translucency (2 mm), visible nasal bone, and normal 16-week anatomy scan, the probability of a healthy baby is extremely high—approximately 98% or greater—even with a non-informative NIPT result. 1

Understanding Your Screening Results

Your Favorable Risk Profile

Your baseline risk is already very low due to several protective factors:

• Maternal age 28 years: Your age-related risk for Down syndrome is substantially lower than the traditional screening cutoff (equivalent to age 35, which carries a first-trimester risk of approximately 1:200) 2

• Normal nuchal translucency (2 mm): An NT measurement of 2 mm falls well below the concerning threshold of 3.0-3.5 mm. Pregnancies with NT <2.0 mm have the lowest risk of chromosomal anomalies, with a baseline prevalence of only 0.5% 3

• Visible nasal bone: The presence of a nasal bone is highly reassuring, as absent nasal bone is a highly predictive marker of trisomy 21 (occurring in approximately 42% of affected fetuses) 4

• Normal 16-week anatomy scan: This is critically important, as approximately 90% of chromosomal abnormalities missed by NIPT are detected through structural anomalies on ultrasound 5

The Non-Informative NIPT Result

A "zero PPV, zero Z-score" NIPT result typically indicates a no-call or failed test, which occurs in approximately 1% of samples, most commonly due to insufficient fetal fraction 1

Important context about no-call results:

• While some studies have shown higher rates of chromosomal disorders in no-call pregnancies, other studies have not confirmed this association 1

• The ACMG and ACOG recommend offering diagnostic testing (amniocentesis) to individuals with no-call results, but this recommendation must be interpreted in the context of your other reassuring findings 1

• No-call results can be associated with maternal factors including obesity, anticoagulant use, or autoimmune disorders, rather than fetal abnormalities 1

Risk Stratification Based on Your Complete Profile

What the Evidence Shows

When all screening parameters are normal (as in your case), the residual risk is remarkably low:

• After normal 20-week ultrasound with normal karyotype: Studies show a 98% chance of a healthy baby, even when NT was initially elevated 6

• Your case is even more favorable because your NT was never elevated—it was completely normal at 2 mm 3

• Detection of missed abnormalities: Only 9% of chromosomal anomalies not detected by gwNIPT had enlarged NT; the vast majority (51%) were detected by structural abnormalities on ultrasound, which you do not have 5, 7

Specific Risks That Remain Low

For conditions NIPT cannot detect (microdeletions, triploidy):

• These represent only 7.7% of all chromosomal abnormalities in pregnancies undergoing invasive testing 5

• Enlarged NT (>3.0 mm) only detected 9% of these "missed cases," and your NT is normal 5, 7

• The optimal NT threshold for detecting abnormalities missed by NIPT is 3.5 mm, which provides the highest positive predictive value; your measurement of 2 mm is well below this 7

For cardiac defects (which can occur with normal chromosomes):

• With NT <2.0 mm, the incidence of major congenital heart defects is 1.9 per 1,000 pregnancies 8

• Your normal 16-week anatomy scan further reduces this concern 8

Clinical Recommendation

You can be highly reassured without proceeding to amniocentesis, given:

1. Your comprehensive screening profile is overwhelmingly normal
2. The single abnormal finding (failed NIPT) is most likely technical rather than fetal in origin
3. The probability of a healthy baby exceeds 98% based on your normal ultrasound findings alone 6

Optional Next Steps

If you desire additional reassurance despite the favorable prognosis:

• Repeat NIPT at a later gestational age (when fetal fraction naturally increases): This provides a result 75-80% of the time 1

• Detailed fetal echocardiography: Consider if you want specific cardiac reassurance, though risk remains very low 8

• Amniocentesis: Remains an option if you require definitive chromosomal diagnosis, but the yield is expected to be very low given your normal ultrasound findings 1

Critical Caveats

• Continue routine prenatal care with standard anatomy ultrasounds, as structural abnormalities remain the most sensitive indicator of chromosomal issues not detected by NIPT 5

• Failed NIPT has been associated with low PAPP-A and early growth restriction in some cases; ensure these parameters are monitored 5

• If any new structural abnormalities or growth concerns emerge on subsequent ultrasounds, diagnostic testing should be reconsidered 9, 5