Is there a nuchal translucency millimeter measurement above which there is no added benefit from first trimester serum screening?
OBJECTIVE
The purpose of this study was to evaluate whether there is a nuchal translucency (NT) measurement, independent of gestational age, above which immediate diagnostic testing should be offered without waiting for first trimester serum markers.


METHODS
Thirty-six thousand one hundred twenty patients had successful measurement of simple NT at 10 3/7 to 13 6/7 weeks and had first trimester serum screening. No risks were reported until second trimester serum screening was completed.


RESULTS
Thirty-two patients (0.09%) had NT > or = 4.0 mm; the lowest combined first trimester trisomy 21 risk assessment in euploid cases was 1 in 8 and among aneuploidy cases was 7 in 8. One hundred twenty-eight patients (0.3%) had simple NT > or = 3.0 mm: the lowest combined first trimester trisomy 21 risk assessment of any patient in this group was 1 in 1479 and the lowest risk assessment among aneuploid cases was 1 in 2. Ten patients (8%) had first trimester trisomy 21 risk assessments lowered to less that 1:200 and none of these 10 cases had an abnormal outcome.


CONCLUSIONS
During first trimester Down syndrome screening, whenever an NT measurement of 3.0 mm or greater is obtained there is minimal benefit in waiting for serum screening results, and no benefit for NT of 4.0 mm or greater. Differentiation between cystic hygroma and enlarged simple NT (> or = 3.0 mm) is now a moot point as both are sufficiently high risk situations to warrant immediate CVS.
Comstock
Christine H
CH
Division of Fetal Imaging, Department of Obstetrics and Gynecology, William Beaumont Hospital, Royal Oak, MI 48073, USA. ccomstock@beaumont.edu
Malone
Fergal D
FD
Ball
Robert H
RH
Nyberg
David A
DA
Saade
George R
GR
Berkowitz
Richard L
RL
Ferreira
Jose
J
Dugoff
Lorraine
L
Craigo
Sabrina D
SD
Timor-Tritsch
Ilan E
IE
Carr
Stephen R
SR
Wolfe
Honor M
HM
Bianchi
Diana W
DW
D'Alton
Mary E
ME
D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D018570:Risk Assessment
D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A