What is the recommended treatment for latent syphilis in pregnant women?

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Last updated: June 27, 2025View editorial policy

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From the Guidelines

The recommended treatment for latent syphilis in pregnant women is penicillin G, with the specific regimen depending on the stage and duration of the infection. For early latent syphilis (infection less than one year), a single dose of benzathine penicillin G 2.4 million units intramuscularly is recommended 1. For late latent syphilis (infection greater than one year) or latent syphilis of unknown duration, the recommended regimen is benzathine penicillin G 2.4 million units intramuscularly once weekly for three consecutive weeks (total 7.2 million units) 1.

Key Considerations

  • Penicillin is the only proven effective treatment for preventing maternal transmission to the fetus and treating fetal infection 1.
  • If the patient has a penicillin allergy, desensitization followed by penicillin treatment is necessary, as alternative antibiotics like doxycycline or tetracycline are contraindicated during pregnancy 1.
  • After treatment, follow-up serologic testing is essential to ensure treatment effectiveness, typically at 3,6, and 12 months 1.
  • The importance of penicillin treatment stems from its ability to cross the placenta and treat the fetus, preventing congenital syphilis which can cause severe birth defects, stillbirth, or neonatal death 1.

Special Situations

  • For women with primary, secondary, or early latent syphilis, some experts recommend an additional dose of benzathine penicillin 2.4 million units IM one week after the initial dose 1.
  • Ultrasonographic signs of fetal syphilis indicate a greater risk for fetal treatment failure, and such cases should be managed in consultation with obstetric specialists 1.

From the Research

Treatment of Latent Syphilis in Pregnant Women

The recommended treatment for latent syphilis in pregnant women is crucial to prevent adverse pregnancy outcomes and congenital syphilis.

  • Benzathine penicillin G is the recommended treatment for syphilis in pregnancy, with a dosage of 2.4 million U 2.
  • For people with late latent and unknown duration stages, 3 injections of benzathine penicillin G at 1-week intervals are recommended 3.
  • The effectiveness of benzathine penicillin regimen in the treatment of syphilis in pregnancy has been confirmed, with a regimen of 2.4 million units weekly for 3 consecutive weeks being clinically effective for prevention of congenital syphilis 4.

Treatment Completion and Benzathine Penicillin Need

  • Completion of 3 benzathine penicillin G injections in pregnant women with late latent or unknown duration syphilis is crucial, with a completion rate of 68.7% reported in one study 3.
  • The need for benzathine penicillin for the treatment of pregnant women diagnosed with syphilis during antenatal care in high-morbidity countries is high, with an estimated 351,016 doses needed annually 5.

Special Considerations

  • Penicillin desensitization can be safely carried out in allergic pregnant women with syphilis, allowing them to receive benzathine penicillin G treatment 6.
  • Initiatives to ensure a stable and adequate supply of benzathine penicillin for treatment of maternal syphilis are important for congenital syphilis prevention 5.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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