A pregnant female infected with Rubella. Which of the following immunoglobulin is produced by in-utero infection?

IgM is the main immunoglobulin produced early in the primary immune response. IgM is present on the surface of viually all uncommitted B cells. It is the most efficient immunoglobulin in agglutination, complement fixation, and other antigen-antibody reactions and is impoant also in defense against bacteria and viruses. It can be produced by a fetus undergoing an infection. As it is not transpoed across the placenta, the presence of IgM in the fetus or newborn indicates intrauterine infection and its detection is useful in the diagnosis of congenital infections such as syphilis, rubella, HIV infection. Since its interaction with antigen can involve all ten binding sites, it has the highest avidity of all immunoglobulins. Ref: Brooks G.F., Carroll K.C., Butel J.S., Morse S.A., Mietzneron T.A. (2010). Chapter 8. Immunology. In G.F. Brooks, K.C. Carroll, J.S. Butel, S.A. Morse, T.A. Mietzneron (Eds), Jawetz, Melnick, & Adelberg's Medical Microbiology, 25e.