First-trimester screening for trisomy 21 combining biochemistry and ultrasound at individually optimal gestational ages. An interventional study.
OBJECTIVE
To assess the effectiveness of the Combined Test in the prenatal detection of trisomy 21 in the general pregnant population using a new timing for the screening approach.


METHODS
First-trimester maternal serum biochemical markers (pregnancy-associated plasma protein-A and free-beta hCG) were determined in maternal serum at 7 to 12 weeks. Fetal nuchal translucency and gestational age were assessed at the 10- to 14-week ultrasound scan. A combined risk was estimated and delivered to the women the same day. When the risk was 1:250 or above, chorionic villus sampling was offered.


RESULTS
Mean gestational age at biochemistry was 9.4 weeks, being 12.3 at ultrasound. In the 2780 studied pregnancies with a complete follow-up, observed detection rates were 88% (7/8) for trisomy 21 and 75% (3/4) for trisomy 18, with a 3.3% (92/2765) false-positive rate.


CONCLUSIONS
The Combined Test, assessing biochemistry and ultrasound at individually optimal ages in the first trimester, showed an 88% detection rate for trisomy 21 with a remarkably reduced false-positive rate (3.3%).
Prenatal Diagnosis Unit, Institute of Gynecology, Obstetrics and Neonatology, Hospital Clinic, University of Barcelona Medical School, Barcelona, Catalonia, Spain. aborrell@medicina.ub.es
Antoni
A
Borrell
Elena
E
Casals
Albert
A
Fortuny
M Teresa
MT
Farre
Anna
A
Gonce
Aurora
A
Sanchez
Anna
A
Soler
Vicençc
V
Cararach
Joan A
JA
Vanrell
D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D002887:Chromosomes, Human, Pair 18; D002891:Chromosomes, Human, Pair 21; D004314:Down Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000196:embryology; D005189:False Positive Reactions; D005260:Female; D005865:Gestational Age; D006801:Humans; D008875:Middle Aged; D048208:Nuchal Translucency Measurement / Q000379:methods; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011296:Prenatal Diagnosis; D014314:Trisomy / Q000175:diagnosis*; D016216:Ultrasonography, Prenatal
D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A