<prompt> Treponema pallidum crosses placentaAfter 36 weeksAfter 28 weeksAfter 2nd trimesterAt any stage of pregnancy  <response>: Transmission of Treponema pallidum from an infected woman to her fetus across the placenta may occur at any stage of pregnancy, but the lesions of congenital syphilis usually develop after the 4th month of gestation, when fetal immunologic competence begins to develop. Ref : Ananthanarayana textbook of Microbiology 9th edition Pgno : 372 