BACKGROUND: Interpretation of positive cytomegalovirus (CMV) immunoglobulin M (IgM) in the first trimester of pregnancy is ill-defined. We aimed to quantify the risk of fetal transmission in women with positive CMV IgM in the first trimester. METHODS: A retrospective cohort of women (2009-2011) was tested for CMV immunoglobulin G (IgG) and IgM before 14 weeks of gestation. IgG avidity was tested with 2 assays (LIAISON and VIDAS). CMV polymerase chain reaction (PCR) was done in maternal serum, amniotic fluid, or neonatal urine at birth. RESULTS: A total of 4931 consecutive women were screened; 201 presented with positive or equivocal IgM and with high, intermediate, or low IgG avidity in 58.7%, 18.9%, and 22.3%, respectively. In 72 women with low or intermediate avidity, fetal transmission was 23.6%. In multivariate analysis, positive CMV PCR in maternal serum, decreasing avidity index with both LIAISON and VIDAS, and low IgG titers were all associated with fetal transmission (odds ratio [OR], 12.38 [95% confidence interval {CI}, 1.77-86.33], P = .011; OR, 0.16 [95% CI, .03-.95], P = .044; OR, 0.54 [95% CI, .11-.88], P = .028; and OR, 0.27 [95% CI, .29-.84], P = .010, respectively). CONCLUSION: This study demonstrates a significant association between the risk of vertical transmission and the avidity index combined with CMV PCR in maternal serum or IgG titers. This allows calculation of incremental risk of fetal transmission upon which informed choice can be based and could lead to a better pickup rate of fetal infection while decreasing unnecessary invasive procedures.
BACKGROUND: Interpretation of positive cytomegalovirus (CMV) immunoglobulin M (IgM) in the first trimester of pregnancy is ill-defined. We aimed to quantify the risk of fetal transmission in women with positive CMV IgM in the first trimester. METHODS: A retrospective cohort of women (2009-2011) was tested for CMV immunoglobulin G (IgG) and IgM before 14 weeks of gestation. IgG avidity was tested with 2 assays (LIAISON and VIDAS). CMV polymerase chain reaction (PCR) was done in maternal serum, amniotic fluid, or neonatal urine at birth. RESULTS: A total of 4931 consecutive women were screened; 201 presented with positive or equivocal IgM and with high, intermediate, or low IgG avidity in 58.7%, 18.9%, and 22.3%, respectively. In 72 women with low or intermediate avidity, fetal transmission was 23.6%. In multivariate analysis, positive CMV PCR in maternal serum, decreasing avidity index with both LIAISON and VIDAS, and low IgG titers were all associated with fetal transmission (odds ratio [OR], 12.38 [95% confidence interval {CI}, 1.77-86.33], P = .011; OR, 0.16 [95% CI, .03-.95], P = .044; OR, 0.54 [95% CI, .11-.88], P = .028; and OR, 0.27 [95% CI, .29-.84], P = .010, respectively). CONCLUSION: This study demonstrates a significant association between the risk of vertical transmission and the avidity index combined with CMV PCR in maternal serum or IgG titers. This allows calculation of incremental risk of fetal transmission upon which informed choice can be based and could lead to a better pickup rate of fetal infection while decreasing unnecessary invasive procedures.