In 2023, Australia recorded its highest-ever case numbers of both syphilis and congenital syphilis, with 6,566 cases of syphilis and 20 cases of congenital syphilis, tragically resulting in 10 infant deaths. As of 6 August 2025, the trajectory remains concerning, with 3,546 syphilis cases and 11 congenital syphilis cases already reported – four of which have resulted in death.¹,³

In New Zealand, syphilis cases have surged from 320 in 2016 to 775 in 2024 – a staggering 142% increase. Congenital syphilis cases also rose from one in 2016 to six in 2024.⁴ Globally, the United States has seen a dramatic 1,059% increase in congenital syphilis rates between 2012 and 2023, with 105.8 cases per 100,000 live births reported in 2023.⁵

Congenital syphilis is a potentially devastating condition, with mortality rates reaching up to 30%. Survivors may suffer long-term complications including skeletal deformities and permanent neurological deficits.²

National Response in Australia

The Australian Government’s response is outlined in the National Strategic Approach for Responding to Rising Rates of Syphilis (2021), which prioritizes three key areas – most notably, a focus on women of reproductive age and the elimination of congenital syphilis.³ On 7 August 2025, the Chief Medical Officer declared syphilis a ‘Communicable Disease Incident of National Significance.’¹

Impact of Syphilis in Pregnancy and Congenital Syphilis

Syphilis is caused by the sexually transmitted spirochete Treponema pallidum. It may present with painless genital chancres (primary infection) or a rash (secondary infection), but many cases are asymptomatic and classified as early or late latent infections. Alarmingly, up to 50% of infected pregnant women are asymptomatic,¹⁰ underscoring the importance of routine and repeated testing during pregnancy.

Untreated syphilis in pregnancy is associated with serious adverse outcomes: up to 35% rates of premature birth, nearly 30% risk of low birth weight, 66% of newborns requiring neonatal ICU admission, and stillbirth rates of up to 10%.¹¹

Vertical transmission can occur at any stage of pregnancy, with the highest risk (up to 70%) during primary, secondary, or early latent infection.¹⁰ Infection acquired later in pregnancy is associated with worse outcomes for both mother and child.

Congenital syphilis is classified as:

• Early congenital syphilis: Appears within the first two years of life, often within the first four months. Symptoms are non-specific and may mimic other infections – anaemia, thrombocytopenia, hepatomegaly, lymphadenopathy, persistent rhinitis, and maculopapular rash.²˒⁷
• Late congenital syphilis: Symptoms emerge after two years and may include long-term sequelae such as osteolytic bone lesions, cranial nerve palsies, seizures, visual impairment or blindness, and sensorineural deafness.

Crucially, appropriate treatment of syphilis during pregnancy, completed at least 30 days before delivery, can prevent congenital syphilis.

Updated Guidelines for Syphilis Testing in Pregnancy

In November 2024, Australia updated its national syphilis guidelines to provide clearer direction for managing syphilis in pregnancy.⁶ Key recommendations include:

• Routine testing at three points during pregnancy:
  • First antenatal visit
  • 26–28 weeks gestation
  • 36 weeks or at delivery (whichever is earlier)
• High-risk groups – including women under 20, those using illicit substances, or receiving minimal antenatal care – should receive additional and opportunistic testing, with at least one test at delivery.⁶˒¹¹

Other significant updates:

• Placental testing: All treated women must have placental tissue sent for histopathology and syphilis PCR, regardless of treatment adequacy.
• Paired serology: Maternal and neonatal serology, including syphilis IgM, should be collected at delivery.
• Partner management: Contact tracing and treatment of all partners is essential to prevent reinfection during pregnancy.

Treatment: Benzathine penicillin remains the only acceptable therapy during pregnancy. In cases of documented penicillin allergy, referral for desensitisation is recommended.

• Early syphilis (symptomatic or early latent): Single dose of 2.4 million IU (1.2 million IU IM to each buttock).
• Late latent syphilis: Three doses of 2.4 million IU, administered at seven-day intervals.

The definition of appropriate treatment includes:

• Accurate staging of infection
• Correct antibiotic, dose, and frequency
• Four-fold reduction in RPR titre
• Completion of treatment more than 30 days before delivery

If these criteria are not met, the newborn remains at risk for congenital syphilis and should be evaluated in consultation with a specialist paediatrician.

Due to the complexity of syphilis serology and treatment protocols, the guidelines strongly recommend involving specialist services – such as Infectious Diseases or clinicians experienced in syphilis management – for all cases of maternal infection.

Summary

Congenital syphilis is entirely preventable with timely diagnosis and appropriate treatment during pregnancy. Eliminating this condition requires:

• Raising awareness of the changing epidemiology of syphilis in pregnant women and women of reproductive age.
• Disseminating updated guidelines and promoting increased testing during pregnancy and at delivery.
• Developing models of care that engage high-risk women to ensure optimal maternal and neonatal outcomes.