Detection of sonographic markers of fetal aneuploidy depends on maternal and fetal characteristics.
OBJECTIVE
The purpose of this study was to determine factors that influence the detection rate of sonographic markers of fetal aneuploidy (SMFA).


METHODS
We reviewed the sonographic images of 160 consecutive second-trimester trisomic fetuses for the presence of SMFA, either structural anomalies or sonographic soft markers.


RESULTS
One hundred forty-nine (93.1%) records were complete and analyzed; 78 cases (52.3%) were identified with 1 or more SMFA. Sonographic markers of fetal aneuploidy were detected in 42.7%, 75.0%, and 90.9% of trisomies 21, 18, and 13, respectively (P<.005). The detection rate of SMFA had a positive linear correlation with gestational age (adjusted R(2)=0.64; P<.002). Sonographic markers of fetal aneuploidy were detected in 43.7% of fetuses of less than 18.0 weeks' gestation and 64.5% of fetuses of 18.0 weeks' gestation or greater (likelihood ratio=6.4; P<.01). Sonographic markers of fetal aneuploidy were detected in 23.5% of patients with suboptimal image quality versus 58.3% of the others (likelihood ratio=7.5; P<.05). The rate of structural malformation was similar between the male and female fetuses, whereas that of soft markers was 49.4% in male and 30.0% in female fetuses (odds ratio=2.3; range, 1.2-4.5; P<.02). Factor analysis showed that some soft markers and some structural anomalies tended to appear together.


CONCLUSIONS
The type of fetal trisomy, gestational age, sex, and quality of images influence the detection rate of SMFA. The highest detection rate for SMFA in the second trimester is at or above 18 weeks' gestational age. Certain markers are detected in clusters. These findings may explain, in part, the variability in reported rates of detection of SMFA among trisomic fetuses. These findings need to be prospectively tested in the general population of pregnancies for applicability to sonographic risk calculations for fetal trisomies.
Taslimi
M Mark
MM
Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Stanford University Medical Center, Stanford, CA 94305-5317, USA. mtaslimi@stanford.edu
Acosta
Reinaldo
R
Chueh
Jane
J
Hudgins
Louanne
L
Hunter
Kennith
K
Druzin
Maurice L
ML
Chitkara
Usha
U
D000782:Aneuploidy; D002882:Chromosomes, Human, Pair 13; D002887:Chromosomes, Human, Pair 18; D004314:Down Syndrome; D005163:Factor Analysis, Statistical; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012189:Retrospective Studies; D014314:Trisomy / Q000175:diagnosis*; D016216:Ultrasonography, Prenatal