Out of 19,435 participants, 6510 (33.50%) showed IgG (−) and IgM (−) results, of which, 4082 were retested for IgG and IgM antibodies; 47 (1.15%) showed IgG and/or IgM seroconversion, being considered as having a primary infection after the first trimester of pregnancy. Here, CD40LG is linked to infection.