Table 1.

Classification of Maternal Cytomegalovirus Infection in Pregnancy

Classification	Summary
Confirmed primary	First blood sample in pregnancy CMV IgG negative and subsequent sample CMV IgG positive (seroconversion confirmed by retesting of samples in pair) (n = 48); or IgG negative on single antenatal blood sample and infant born with confirmed congenital infection (n = 11);
Presumed primary	First antenatal blood sample CMV IgM positive (n = 23)
Confirmed nonprimary	CMV IgG positive on a blood sample collected before conception (eg, in a previous pregnancy) (n = 21)
Presumed nonprimary	CMV IgG positive/IgM negative on initial blood sample taken in the first trimester of pregnancy (n = 23); or a 4-fold or greater rise in CMV IgG titer in paired samples without the appearance of CMV IgM (n = 1)
Unclassified	Test results not fulfilling above criteria, or no maternal samples available (n = 49)

Abbreviations: CMV, cytomegalovirus; IgG, immunoglobulin G; IgM, immunoglobulin M.