Infectious causes of recurrent pregnancy loss.

Current knowledge supports the view that nonviral organisms may be responsible for repeated pregnancy wastage through chronic or recurrent occupancy in the maternal reproductive tract. However, two forms of evidence that would establish more clearly such a role lack for all of the organisms presented: recovery of the same organism from the products of conception in successive pregnancy losses, and demonstration of improved pregnancy outcome following specific treatment in a randomized prospective controlled trial. While acquisition of such data is scientifically justified, the necessary study designs may be viewed as unethical if the body of information derived from circumstantial cases and therapeutic trials using historical controls only continues to shape clinical opinion. Further confirmation of a specific role in pregnancy wastage for any of these organisms eventually will have to address the mysterious discrepancy between the prevalence of colonization and the incidence of sporadic and recurrent abortion purportedly due to the organism.