Skeletal abnormalities in fetuses with Down's syndrome: a radiographic post-mortem study.
OBJECTIVE
To evaluate skeletal abnormalities on post-mortem radiographs of fetuses with Down's syndrome.


METHODS
Biometrical and morphological criteria, which are used for US prenatal detection of trisomy 21, were assessed. Limb long bones, biparietal diameter (BPD)/occipito-frontal diameter (OFD) ratio, ossification of nasal bones and appearance of the middle phalanx of the fifth digit (P2) in 60 fetuses with Down's syndrome were analysed and compared with 82 normal fetuses matched for gestational age (GA) from 15 to 40 weeks' gestation (WG).


RESULTS
We observed reduced growth velocity of limb long bones during the third trimester in both groups, but the reduction was more pronounced in the trisomic group. Brachycephaly was found as early as 15 WG in Down's syndrome and continued throughout gestation (sensitivity 0.28, specificity 1). Ossification of the nasal bones, which can be detected in normal fetuses from 14 WG, was absent in one quarter of trisomic fetuses, regardless of GA. The middle phalanx of the fifth digit was evaluated by comparison with the distal phalanx (P3) of the same digit. We found that P2 was not ossified in 11/31 trisomic fetuses before 23 WG, and was either not ossified or hypoplastic in 17/29 cases after 24 WG (sensitivity 0.56, specificity 1).


CONCLUSIONS
Three key skeletal signs were present in trisomic fetuses: brachycephaly, absence of nasal bone ossification, and hypoplasia of the middle phalanx of the fifth digit. All these signs are appropriate to prenatal US screening. When present, they fully justify determination of the fetal karyotype by amniocentesis.
Stempfle
N
N
Department of Radiology, R. Debré Hospital, Paris, France.
Huten
Y
Y
Fredouille
C
C
Brisse
H
H
Nessmann
C
C
D001842:Bone and Bones / Q000002:abnormalities* / Q000000981:diagnostic imaging; D001133:Bones of Upper Extremity / Q000000981:diagnostic imaging / Q000196:embryology; D002102:Cadaver; D016022:Case-Control Studies; D002508:Cephalometry; D016009:Chi-Square Distribution; D004314:Down Syndrome / Q000000981:diagnostic imaging / Q000196:embryology*; D005333:Fetus / Q000000981:diagnostic imaging*; D005385:Fingers / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000196:embryology; D005624:Frontal Bone / Q000000981:diagnostic imaging / Q000196:embryology; D005865:Gestational Age; D006801:Humans; D007867:Leg Bones / Q000000981:diagnostic imaging / Q000196:embryology; D009295:Nasal Bone / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000196:embryology; D009777:Occipital Bone / Q000000981:diagnostic imaging / Q000196:embryology; D010012:Osteogenesis; D010294:Parietal Bone / Q000000981:diagnostic imaging / Q000196:embryology; D012372:ROC Curve; D011859:Radiography; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D012886:Skull / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000196:embryology