During antenatal check up, a primigravida is found to be positive for treponema pallidum infection. She is worried about her child. At which week treponema pallidum infection will transfer to the fetus?

Treponema pallidum enters the fetal circulation after the 20th week with the disappearance of Langhans layer (cytotrophoblast) in the villi. The basic pathology is obliterative endaeritis. The placenta and villi become bulky. Depending upon the intensity and time of occurrence of the infiltration, the fate of the fetus will be as follows: Aboion Preterm bih Intrauterine deaths leading to either a macerated or a fresh stillbih Delivery of a highly infected baby with early neonatal death Survival with congenital syphilis Ref: Textbook of Obstetrics by D C Dutta, 6th edition, Page 293.