Ossification sequence in infants who die during the perinatal period: population-based references.
OBJECTIVE
To determine population-based references for the relationships between the presence of ossification centers and gestational age and skeletal length measurements among infants who die during the perinatal period, as well as to evaluate the possible influence of intrauterine growth restriction on ossification stage.


METHODS
During an 11-year period, nearly all infants who died perinatally in a well-defined geographic area routinely underwent radiography with a standardized technique. The presence of visible secondary ossification centers in the singletons (n = 495) was evaluated. Cluster analysis was used to identify stages of ossification; a sequential appearance of secondary ossification centers was assumed. Comparisons were made with Wilks lambda between male and female infants and between infants who were presumed to have growth restriction and those who were not. Reference ranges for the presence of ossification centers were calculated for interquartile ranges of femur length and gestational age.


RESULTS
Eight clusters of ossification defining different stages of ossification of the pelvis, hindfeet, and knees were identified. The sequential clusters outlined well-defined intervals of femur length and gestational age. Bone lengths, birth weight, and gestational age within ossification clusters did not differ between the sexes (Wilks lambda = 0.989, P =.532) or according to whether growth restriction was presumed to exist (Wilks lambda = 0.958, P =.481).


CONCLUSIONS
The reference diagrams calculated with this method indicate relationships between ossification sequence and both gestational age and skeletal length measurements.
D001724:Birth Weight; D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000196:embryology; D005260:Female; D005313:Fetal Death / Q000000981:diagnostic imaging; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging; D005333:Fetus / Q000000981:diagnostic imaging*; D005529:Foot Bones / Q000000981:diagnostic imaging / Q000196:embryology; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000401:mortality; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000196:embryology; D008297:Male; D010012:Osteogenesis; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000196:embryology; D011859:Radiography