Treatment for Pregnant Women with Syphilis
Pregnant women with positive RPR and confirmatory treponemal antibody tests should be treated with parenteral benzathine penicillin G as the only proven effective therapy for preventing maternal transmission to the fetus and treating fetal infection.
Diagnostic Confirmation
- A positive RPR (Rapid Plasma Reagin) test with confirmatory positive treponemal antibody test (such as FTA-ABS or TP-PA) confirms the diagnosis of syphilis 1
- Both tests are necessary as false-positive nontreponemal tests can occur with various medical conditions 1
Treatment Regimen
Primary Treatment
The treatment depends on the stage of syphilis:
Early syphilis (primary, secondary, or early latent syphilis <1 year):
Late latent syphilis (>1 year duration) or syphilis of unknown duration:
- Benzathine penicillin G 2.4 million units IM weekly for three consecutive weeks 1
Penicillin Allergy Management
- Penicillin is the only proven effective therapy for syphilis during pregnancy 1
- Pregnant women with penicillin allergy should undergo penicillin desensitization followed by appropriate penicillin therapy 1
- Alternative antibiotics (erythromycin, azithromycin) are not recommended as they cannot reliably cure an infected fetus 1, 3
- A study showed that azithromycin failed to prevent congenital syphilis in five cases 3
Follow-Up Monitoring
- Serologic titers should be checked monthly until adequate treatment response is confirmed 1
- An appropriate response includes:
- Follow-up tests should use the same nontreponemal test (RPR or VDRL) as initially used, preferably by the same laboratory 1
Special Considerations
Jarisch-Herxheimer Reaction
- Women treated for syphilis during the second half of pregnancy are at risk for premature labor or fetal distress due to the Jarisch-Herxheimer reaction 1, 4
- Patients should be advised to seek medical attention if they notice changes in fetal movement or contractions after treatment 1
- Despite this risk, treatment should not be delayed as it is necessary to prevent further fetal damage 1
HIV Testing
- All patients with syphilis should be tested for HIV 1
- HIV-infected patients may have atypical serologic responses but generally respond well to standard treatment regimens 1
Prevention of Congenital Syphilis
- All pregnant women should be screened for syphilis at their first prenatal visit 1
- Women at high risk for syphilis should be retested in the third trimester and at delivery 1
- No infant should leave the hospital without the serologic status of the mother having been determined at least once during pregnancy 1
Evidence for Multiple Doses
Research indicates that a single dose of benzathine penicillin G may be insufficient for treating syphilis during pregnancy:
- A study from South Africa showed that one injection of 2.4 million units of benzathine penicillin G resulted in lower birth weight, increased prematurity, and higher perinatal mortality compared to two or three weekly injections 2
- Treponemicidal coverage of 3 weeks or less resulted in worse outcomes compared to coverage lasting longer than 3 weeks 2
Common Pitfalls to Avoid
- Using alternative antibiotics: Erythromycin and azithromycin cannot reliably cure fetal infection 1, 3
- Inadequate follow-up: Failure to monitor serologic response can miss treatment failures 1
- Insufficient treatment: Single-dose therapy may be inadequate, especially in early pregnancy or with high titers 2
- Switching between different nontreponemal tests: This can lead to inaccurate comparisons of titers 1
- Delaying treatment: Despite risks of Jarisch-Herxheimer reaction, treatment should not be delayed 1