<prompt> Incubation period of syphilis9-90 days9-18 days80-90 days10 days  <response>: Ans. a 9-90 days. Ref. Harrison, Principles of Internal Medicine, 18th Chapter 169. SyphilisSYPHILIS T. Pallidum enters foetal circulation after 20th week of gestation with disappearance of cytotrophoblast in villi.0 Basic pathology is obliterative endarteritis. Placenta becomes bulky and spirochaete can hardly be found in placenta. Spirochaete can however be detected from maculopapular rash in baby. Irrespective of the serology, treatment should be repeated in subsequent pregnancies. Incubation period of syphilis is 9-90 days 