Congenital syphilis in Switzerland: a national retrospective study

Congenital syphilis (CS) is a rare complication of syphilis. Vertical transmission
may occur at any time of pregnancy. Its incidence has been increasing
worldwide. CS notification has been used for years in Switzerland but do not
provide details on mothers or new-born. We assessed the estimated prevalence
of CS in Switzerland, and aimed to identify maternal risk factors associated with
syphilis in pregnancy as well as children outcome.
A total of 147 pregnant women and 102 children were included. A history of treated syphilis was known for 44,2% of the mothers corresponding to serologic scar. The other 55,8% were identified by the screening during pregnancy. Diagnosis of syphilis was made at the first trimester in 53,7%, second trimester in 28,6%, and 3rd trimester in 12,9% of cases. Only 3 babies were diagnosed with congenital syphilis as defined by the European guidelines. Their mothers were diagnosed late in the pregnancy during the 3rd trimester. Maternal risk profiles were a foreign origin (93,2% of mothers), lack of healthcare insurance (24,5%), no occupation (37,4%), drug use (4,8%), co-infection with other sexually transmitted infections (23,8%) and a late first antenatal consultation (12,9%). Children exposed in utero to syphilis had a higher preterm delivery rate (18,7% against 6,4% in Switzerland in 2021).
In conclusion, CS remains rare in Switzerland. However, we showed a maternal risk profile that warrant an active prevention. A specialized multidisciplinary follow up is needed to improve surveillance and healthcare in this vulnerable population.
This work has been presented as a poster at the 36th International Union Against Sexually Transmitted Infections congress and will also be presented at the 42nd Annual Meeting of the European Society of Pediatrics Infectious Diseases Congress.