Notification rates for syphilis in women of reproductive age and congenital syphilis in Australia, 2011-2021: a retrospective cohort analysis of national notifications data.

Objectives: To estimate notification rates for infectious syphilis in women of reproductive age and congenital syphilis in Australia.

Study Design: Retrospective cohort study; analysis of national infectious syphilis and enhanced congenital syphilis surveillance data.

Setting, Participants: Women aged 15-44 years diagnosed with infectious syphilis, and babies with congenital syphilis, Australia, 2011-2021.

Main Outcome Measures: Numbers and rates of infectious syphilis notifications, by Indigenous status and age group; numbers and rates of congenital syphilis, by Indigenous status of the infant; antenatal care history for mothers of infants born with congenital syphilis.

Results: During 2011-2021, 5011 cases of infectious syphilis in women aged 15-44 years were notified. The notification rate for Aboriginal and Torres Strait Islander women rose from 56 (95% confidence interval [CI], 45-65) cases per 100 000 in 2011 to 227 (95% CI, 206-248) cases per 100 000 population in 2021; for non-Indigenous women, it rose from 1.1 (95% CI, 0.8-1.4) to 9.2 (95% CI, 8.4-10.1) cases per 100 000 population. The notification rate was higher for Aboriginal and Torres Strait Islander women than for non-Indigenous women (incidence rate ratio [IRR], 23.1; 95% CI, 19.7-27.1), lower for 15-24- (IRR, 0.7; 95% CI, 0.6-0.9) and 35-44-year-old women (IRR, 0.6; 95% CI, 0.5-0.7) than for 25-34-year-old women, and higher in remote regions than in major cities (IRR, 2.7; 95% CI, 2.2-3.8). During 2011-2021, 74 cases of congenital syphilis were notified, the annual number increasing from six in 2011 to a peak of 17 in 2020; the rate was consistently higher among Aboriginal and Torres Strait Islander infants than among non-Indigenous infants (2021: 38.3 v 2.1 per 100 000 live births). The mothers of 32 infants with congenital syphilis (43%) had not received antenatal care.

Conclusions: The number of infectious syphilis notifications for women of reproductive age increased in Australia during 2011-2021, as did the number of cases of congenital syphilis. To avert congenital syphilis, antenatal screening of pregnant women, followed by prompt treatment for infectious syphilis when diagnosed, needs to be improved.