A study found that about 1/4 of all otherwise normal infants have evidence of infantile rickets while still in the womb. It is likely that tens of thousands of infants are being sent home from the hospital with multiple fractures because no one has ever done a study looking for asymptomatic fractures.

Mahon P, et al. Low maternal vitamin D status and fetal bone development: cohort study. J Bone Miner Res. 2010 Jan;25(1):14-9.