Fetal serum β2-microglobulin as a marker for fetal infectious diseases

Objectives To evaluate whether fetal serum beta 2-microglobulin could be used as a marker of fetal cytomegalovirus (CMV) or toxoplasmosis infection. Methods beta 2-microglobulin was retrospectively assayed in fetal serum collected from 64 patients with maternal infectious seroconversion (toxoplasmosis in 49 cases, CMV in 15). Using a beta 2-microglobulin cutoff of 5 mg/L, infection and control groups were compared. Results Fetal serum beta 2-microglobulin was >5 mg/L (5.2-13.5 mg/L) in 12 of the 13 cases with proved fetal toxoplasmosis infection, indicating 90% sensitivity. In the 39 pregnancies with maternal seroconversion but no laboratory signs of fetal infection, fetal serum beta 2-microglobulin was <5 mg/L, indicating 100% specificity. Fetal serum was >5 mg/L (6.3-32 mg/L) in 14 of the 15 cases with proved fetal CMV infection, indicating 93.3% sensitivity. Specificity cannot be evaluated because maternal serum is not routinely screened for CMV during pregnancy. Conclusions Fetal serum beta 2-microglobulin is a reliable marker of fetal CMV or toxoplasmosis infection, which can be used in ambiguous situations. Because this increase is not specific, fetal serum beta 2-microglobulin would potentially be raised in other fetal infections. Copyright (C) 2006 John Wiley & Sons, Ltd.