Factors influencing development of secondary ossification centres in the fetus and newborn. A postmortem radiological study.

Whole body radiographs of 379 consecutive perinatal necropsies were used to determine the presence and diameters of secondary ossification centres in the os calcis, talus, distal femur, proximal tibia, cuboid bone, and proximal humerus. An estimate of the normal development for gestational age was obtained from 164 selected cases. The variation in number and size of bone centres was too wide for accurate estimation of maturity in the individual case, but ossification could be classified as relatively normal, advanced, or retarded, and comparisons made between groups of cases. Retardation of ossification was found mainly in association with males and small-for-dates babies, but also in some congenital malformations such as the trisomy syndromes and some multiple births: retardation was suggested in association with toxaemia of pregnancy, increasing maternal age, and increasing parity. Advanced ossification was mainly related to female babies but was also found in relation to other malformations, especially anencephalus, and was suggested in association with Negro infants.