Syphilis in pregnancy and infant outcomes in Manitoba

Infectious syphilis has been increasing in incidence in Manitoba since 2012, especially in heterosexual women of childbearing age resulting in an increasing number of infants with in utero exposure and who are at risk for congenital syphilis (CS). We aimed to evaluate the impact of syphilis in pregnancy on infants and to describe our experience with CS.

This retrospective 2012 to 2018 cohort study reviewed women with syphilis in pregnancy and short-term infant outcomes. We grouped mother-infant pairs into high risk and low risk for CS and compared their management and outcomes. We also describe our cases of confirmed and possible CS.

Seventy-nine mothers and 80 infants met inclusion criteria. Thirty mother-infant pairs were classified as high risk for CS. Nine of their infants were diagnosed with confirmed CS and four with possible CS. All confirmed CS cases were asymptomatic at birth but two were not recognized to have CS until they later presented with symptoms. One of these infants had negative serologies (treponemal and non-treponemal) at birth, but at 3 months old had reactive serologies. Two months of age was the earliest clearance of maternal treponemal antibodies amongst low-risk infants compared to 6 months in high-risk infants. Most infants who did not have confirmed CS had non-reactive non-treponemal tests by 6 months old.

Our study shows that symptoms and paired maternal-infant non-treponemal titres at birth are not sensitive for diagnosing CS. Serologies can be falsely negative with recent infection. Regardless of investigations or clinical findings, 10 days of intravenous penicillin G should be considered for all high-risk infants.