Echographic signs of trisomy 21 in the second trimester of pregnancy: actual value after analysis of the literature.
OBJECTIVE
To evaluate the interest and to compare the major echographic signs of Down syndrome in the second trimester of pregnancy.


METHODS
A bibliographic research has been performed for most of the echographic signs known and studied until now. For each study and in average for each sign, we have computed its sensitivity, its specificity, its positive and negative predictive values using the results of the different authors. Then, we have compared the benefits/risk ratio for each of these signs: the number of Down syndrome cases detected versus healthy fetus lost due to amniocentesis complications.


RESULTS
The different signs can be ranked according to their benefits/risk ratio from top to bottom as follows: nuchal skinfold thickness, wide space between first and second toe, pyelectasis, large iliac angle, short humerus, short femur, hypoplasia of the middle phalanx of the fifth digit.


CONCLUSIONS
These results suggest that second trimester echographic signs of Down syndrome must be evaluated as a function of the Down syndrome risk in the population under study. The presence of these signs does not always justify an amniocentesis; it should lead to a re-evaluation of the individual risk of a Down syndrome (a chart is given to guide this re-evaluation).
Vautier-Rit
S
S
Clinique de Gynécologie-Obstétrique-Néonatologie, Hôpital Jeanne-de-Flandre, 1, rue Avinée, 59037 Lille Cedex.
Subtil
D
D
Vaast
P
P
Dufour
P
P
Valat
A S
AS
Bourgeot
P
P
Puech
F
F
D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000196:embryology; D005385:Fingers / Q000000981:diagnostic imaging / Q000196:embryology; D006801:Humans; D006811:Humerus; D007085:Ilium / Q000000981:diagnostic imaging / Q000196:embryology; D009333:Neck / Q000000981:diagnostic imaging / Q000196:embryology; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D016216:Ultrasonography, Prenatal