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Syphilis in Pregnancy Penicillin Allergy — SCE Infectious Diseases MCQ

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HardSTIsSyphilis in Pregnancy Penicillin AllergySCE Infectious Diseases

A 30-year-old woman presents with genital ulceration and inguinal lymphadenopathy. She is 34 weeks pregnant. Syphilis serology confirms secondary syphilis (RPR 1:128, positive TPHA). She has a documented severe penicillin allergy (anaphylaxis with cardiovascular collapse). What is the recommended approach?

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Correct answer: C — Penicillin desensitisation followed by Benzathine Penicillin G — penicillin is the ONLY proven treatment to prevent congenital syphilis

In pregnancy, Benzathine Penicillin G is the ONLY antibiotic proven to adequately treat the mother AND prevent congenital syphilis. Doxycycline is contraindicated in pregnancy (teeth/bone). Azithromycin resistance is increasing and it does not reliably cross the placenta. Erythromycin does not achieve adequate fetal levels. For pregnant women with true penicillin anaphylaxis, penicillin desensitisation (performed in a monitored setting) followed by standard Benzathine Penicillin G treatment is mandated by all major guidelines.

Reference: BASHH 2019 – Syphilis; CDC 2021 – Syphilis in pregnancy; BHIVA 2025 – Pregnancy