Incidence and associated factors of congenital syphilis at a tertiary care center in Thailand.

Background: The incidence of congenital syphilis is increasing worldwide, in parallel with the increase of syphilis in the general population.

Objectives: This study aimed to determine the incidence and risk factors for congenital syphilis at a referral tertiary care center in Bangkok, Thailand.

Methods: This is a case-control study using the hospital medical records of neonates born at our hospital, whose mothers had confirmed syphilis during pregnancy or at delivery between 2011 and 2018. Maternal and neonatal data were reviewed. Neonates were categorized into congenital syphilis according to CDC surveillance case definition for congenital syphilis 2015 and the American Academy of Pediatrics Congenital Syphilis 2018: confirmed and probable were assigned to the case group, while possible and less likely congenital syphilis were used as the control group. Factors associated with congenital syphilis were analyzed using univariable and multivariable analysis.

Results: Among 19,558 live births, there were 126 neonates born to mothers with syphilis. Almost 40% of mothers were teenage mothers and 48.4% had inadequate or no syphilis treatment. Forty neonates met the criteria of congenital syphilis giving the incidence of 204 per 100,000 live births (95% confidence interval [CI]: 146-278). Factors associated with congenital syphilis were inadequate treatment of maternal syphilis and preterm birth (adjusted odd ratio [aOR]: 2.69, 95% CI: 1.02-7.11, P = 0.046 and aOR: 2.91; 95% CI: 1.01-8.39, P = 0.049, respectively).

Conclusions: The incidence of congenital syphilis in our institution was high. Factors associated with congenital syphilis were inadequate treatment of maternal syphilis and preterm birth. Improvement of prenatal care should be emphasized.