Patient Profile
- Maternal age:
- 40 years
- Gestational age:
- 13 weeks 1 day (CRL 71 mm)
- Pregnancy:
- G3P0 — singleton, IVF (own oocyte)
- Indication for scan:
- Advanced maternal age, prior NIPT showing low-risk T21/18/13 — additional sonographic risk markers requested
- Examiner credentials:
- FMF-certified sonographer, equipment with appropriate calibration
Summary Overview
Standardized first-trimester ultrasound assessing all four FMF aneuploidy markers (NT, nasal bone, ductus venosus a-wave, tricuspid regurgitation). 4 markers evaluated; 1 mildly abnormal (NT 2.7 mm, just above the 95th percentile for CRL). Biophysical anatomy survey within normal limits for gestational age.
Integrated Risk Modifiers
- Background risk (T21):
- 1:80 at age 40 (a priori) [Snijders RJ, Lancet 1999]
- Post-NIPT risk (T21):
- < 1:10,000 (NIPT result reported low-risk; PPV ≥99%) [ACOG 226, 2020]
- Sonographic adjustment:
- NT 2.7 mm (~95th–97th percentile) — minor likelihood ratio increase
- Final integrated risk:
- Remains low for the major aneuploidies; structural follow-up recommended for non-chromosomal causes of NT elevation
Detailed Marker Analysis
Structural Anatomy Survey (limited at this gestation)
- Skull: normal contour, choroid plexuses symmetric, falx midline
- Spine: ossified, no obvious dysraphism
- Abdominal wall: intact, physiologic midgut herniation has resolved
- Cardiac four-chamber view: identified, axis normal
- Stomach, bladder: visualized
- Limbs: four limbs identified, segments visualized
Detailed cardiac and structural assessment will be more sensitive at the second-trimester anatomy scan (18–22 weeks).
Risk Interpretation
-
Major aneuploidy (T21/18/13)Low (post-NIPT)
NIPT > 99% PPV for these conditions in high-risk maternal age; isolated borderline NT with no additional markers does not meaningfully alter this.
-
Congenital heart defect (CHD)Modest excess
NT in upper range with normal karyotype carries roughly 2–3% absolute CHD risk vs ~0.7% baseline [Souka AP 2005]. Detailed fetal echocardiogram is recommended.
-
Other genetic syndromes (e.g. Noonan, skeletal dysplasias)Low
Most NT > 95th percentile cases with normal karyotype and normal anatomy proceed uneventfully [Bilardo CM 2007]. Optional expanded molecular testing (e.g., Noonan panel) may be discussed.
Analytical Summary & Recommendations
Clinical pattern
NIPT-low-risk pregnancy with isolated borderline NT (2.7 mm) and otherwise reassuring first-trimester aneuploidy markers and structural survey. Aneuploidy risk is robustly low; the relevant residual question is non-chromosomal etiology of the borderline NT.
Recommended next steps
- Detailed fetal anatomy scan at 18–22 weeks with particular attention to cardiac structures
- Fetal echocardiography at ~20–22 weeks (specialist) given upper-range NT
- Discuss optional expanded molecular testing (e.g., chromosomal microarray, Noonan-spectrum gene panel) — optional given low overall residual risk
- Review with maternal-fetal-medicine specialist — joint counseling appropriate given maternal age
- Routine prenatal care otherwise; no immediate intervention required
Key Questions for Your Physician
- Given my normal NIPT, how much should the borderline NT change my plans?
- Should I have a specialist fetal echocardiogram, and when?
- Is expanded genetic testing (microarray, gene panels) recommended in my case?
- What specific structures will be examined at the anatomy scan?
- What signs would prompt earlier follow-up imaging?
What This Means for You
Your first-trimester ultrasound is largely reassuring. Three of the four "early-pregnancy markers" used to refine genetic risk look completely normal, and your previously low-risk NIPT remains the strongest reassurance for Down syndrome and the other major chromosomal conditions.
There is one finding worth following up: the back-of-neck measurement (NT) is just above the typical range (2.7 mm versus a 95th-percentile cutoff of about 2.6 mm at this fetal size). On its own, with everything else normal and a low-risk NIPT, this is not a major concern for chromosomal conditions. However, slightly larger NT measurements are associated with a modestly higher chance of congenital heart defects — for that reason, a specialist fetal heart ultrasound at around 20–22 weeks is recommended.
The full 20-week anatomy scan remains the most informative next step. Your prenatal team will help you decide whether any additional genetic testing would be useful in your case.
High confidence in marker interpretation given FMF-standard examination quality. The borderline NT carries inherent interpretive uncertainty — clinical context (maternal age, low-risk NIPT) and downstream imaging (anatomy scan, fetal echo) refine the picture.
References
- Nicolaides KH. Screening for fetal aneuploidies at 11 to 13 weeks. Am J Obstet Gynecol 2011;204(5):359–369.
- Souka AP, Von Kaisenberg CS, Hyett JA, et al. Increased nuchal translucency with normal karyotype. Am J Obstet Gynecol 2005;192(4):1005–21.
- Bilardo CM, Müller MA, Pajkrt E, et al. Increased nuchal translucency thickness and normal karyotype: time for parental reassurance. Ultrasound Obstet Gynecol 2007;30(1):11–8.
- Cicero S, Curcio P, Papageorghiou A, Sonek J, Nicolaides KH. Absence of nasal bone in fetuses with trisomy 21 at 11-14 weeks of gestation. Lancet 2001;358:1665–7.
- Maiz N, Wright D, Ferreira AF, Syngelaki A, Nicolaides KH. Ductus venosus flow at 11+0 to 13+6 weeks for the prediction of outcome in twin pregnancies. Fetal Diagn Ther 2010;28:104–11.
- Falcon O, Auer M, Gerovassili A, Spencer K, Nicolaides KH. Screening for trisomy 21 by fetal tricuspid regurgitation, nuchal translucency and maternal serum free β-hCG and PAPP-A at 11+0 to 13+6 weeks. Ultrasound Obstet Gynecol 2006;27(2):151–5.
- ACOG Practice Bulletin 226: Screening for Fetal Chromosomal Abnormalities. Obstet Gynecol 2020;136(4):e48–e69.