Jarisch-Herxheimer reaction risk: Warn patient & monitored especially in late pregnancy due to potential for uterine contractions and fetal distress.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Screen
Universal screening at the first prenatal visit (required by law in most jurisdictions).
Rescreen at 28 weeks and at delivery for high-risk patients or those in high-prevalence areas.
Evaluation of any patient presenting with an unexplained maculopapular rash (palms/soles) or painless genital ulcer (chancre).
Mandatory workup for all cases of fetal hydrops or unexplained stillbirth.
Diagnosis Requirements
Diagnosis requires two-stage serologic testing: a nontreponemal test (RPR or VDRL) and a treponemal-specific test (TP-PA or FTA-ABS). A single positive test is insufficient due to potential biological false positives.
Section 2
Formula & Logic
Staging and Treatment Duration
Primary, Secondary, or Early Latent (<1 yr)
Benzathine Penicillin G 2.4M units IM x 1 dose
Late Latent (>1 yr) or Unknown Duration
Benzathine Penicillin G 2.4M units IM QWeek x 3 doses
Neurosyphilis
Aqueous Crystalline Penicillin G 18–24M units/day IV x 10–14 days
The Jarisch-Herxheimer Reaction
An acute febrile response occurring within 24 hours of starting treatment for syphilis. In pregnancy, this may trigger preterm labor or fetal distress (late decelerations) due to the massive release of treponemal lipopolysaccharides. This is NOT a penicillin allergy.
Section 3
Pearls/Pitfalls
Critical Management Pearls
Penicillin G is the ONLY effective treatment for preventing congenital syphilis. No alternatives (e.g., Azithromycin, Doxycycline) are acceptable in pregnancy.
If a pregnant patient is Penicillin-allergic, they MUST be hospitalized for desensitization and then treated with Penicillin.
Treatment is considered "adequate" only if completed ≥30 days prior to delivery.
A 4-fold (two-titer) increase in RPR after treatment indicates reinfection or treatment failure.
Administer first dose of IM Benzathine Penicillin G immediately upon diagnosis.
02
Monitor for Jarisch-Herxheimer reaction (especially if >20 weeks gestation).
03
Repeat RPR/VDRL titers monthly to ensure an appropriate response (expect 4-fold decrease in 6–12 months).
04
Ensure partner is treated to prevent ping-pong reinfection.
05
Notify public health authorities (Mandatory Reportable Disease).
Neonatal Coordination
Notify the pediatric team of maternal stage, treatment dates, and titers. All infants born to mothers with reactive serology require evaluation, even if maternal treatment was considered adequate.
Workowski KA et al. • MMWR Recomm Rep.. 2021;The definitive CDC reference for syphilis staging, dosing, and follow-up protocols.
Evidence for Penicillin Superiority
Efficacy of treatment for syphilis in pregnancy.
Alexander JM et al. • Obstet Gynecol.. 1999;Demonstrated that Penicillin G treatment is 98% effective at preventing congenital syphilis when initiated early.
Section 6
Literature
The Resurgence of a Great Imitator
Syphilis is caused by the spirochete Treponema pallidum. While it was nearly eradicated in the late 20th century, the US has seen a catastrophic 200%+ increase in congenital syphilis cases over the last decade, leading to renewed emphasis on triple-screening during pregnancy.
Historical Context
Before the advent of Penicillin in 1943, syphilis was a leading cause of fetal loss and neonatal disability. It is known as the "Great Imitator" because its clinical manifestations (especially in the secondary stage) can mimic almost any other medical condition.
