We reviewed postmortem radiographs of a number of 2 nd trimester abortuses known to have aneuploidy or neural tube defects, and of 200 second trimester fetuses either delivered spontaneously or aborted for reasons other than fetal abnormality, and considered normal by a perinatal pathologist. Gestational age estimates were based on good menstrual dates where available, on biparietal diameter, or on femoral length. No normal second trimester fetus had coccygeal calcification on radiographs or ultrasound. Four of 7 triploid fetuses had abnormal calcification, in the coccyx in one case. She had cervical cystic hygromas with hydrops, a solitary kidney, and calcification in coccyx, hips and heels.
Ultra sound is unlikely to differentiate between calcification and ossification.
However, coccygeal calcification is not a constant finding in reported cases of chondrodysplasia punctata and related conditions, and its absence does not exclude them. Schutgens RBH, Heymans HSA, Wanders RJA, et al. Curry CJR, Magenis RE, Brown M, et al. Inherited chondrodysplasia punctata due to a deletion of the terminal short arm of an x chromosome. Spranger JW, Opitz JM, Bidder U. Heterogeneity of chondrodysplasia punctata.