3. Fetal Infection
Spirochetes can cross the placenta and infect the fetus from about 14 weeks’ gestation, and the risk of fetal infection increases with gestational age [17]. The manifestations of CS are influenced by gestational age, stage of maternal syphilis, maternal treatment, and immunological response of the fetus [18]. CS can lead to spontaneous abortion, usually after the first trimester, or late-term stillbirth in 30 to 40 percent of cases or premature or term delivery of live infants who may have obvious signs of infection or be fully asymptomatic (approximately two-thirds of liveborn cases) [19]. Placental infection and the reduction in blood flow to the fetus are the most common causes of fetal death. An untreated woman has about 70% of chance of fetal infection during the first 4 years of disease. In 35% of cases, infected fetuses are born alive with CS. Low birth weight can be the only sign of infection. In fact about 60% of liveborns are asymptomatic at birth [20, 21]. CS has been traditionally classified in early congenital syphilis (ECS) and late congenital syphilis (LCS). In ECS signs appear in the first 2 years of life while in LCS signs appear over the first 2 decades. Clinical manifestations of ECS are the result of active infection and inflammation while clinical manifestations of LCS are malformation or stigmata that represent the scars induced by initial lesions of ECS or can be the result of chronic inflammation [2]. After fetal infection occurs, any organ system can be affected because of the widespread spirochetal dissemination.