Treponema pallidum crosses placenta:
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.
After 36 weeks
After 28 weeks
After 2nd trimester
At any stage of pregnancy