Treatment for Pregnant Patients with Rising RPR Titers
Pregnant patients with rising RPR titers should receive immediate retreatment with benzathine penicillin G, with the dosage determined by the stage of syphilis: 2.4 million units IM as a single dose for early syphilis or 2.4 million units IM weekly for 3 consecutive weeks for late latent or unknown duration syphilis. 1
Understanding Rising RPR Titers in Pregnancy
Rising RPR (Rapid Plasma Reagin) titers during pregnancy indicate one of the following scenarios:
- Treatment failure of previous therapy
- Reinfection
- Inadequate initial treatment
This requires prompt intervention as untreated or inadequately treated syphilis can lead to:
- Stillbirth (in up to 25% of cases)
- Premature birth
- Congenital syphilis
- Fetal and perinatal death 2
Diagnostic Approach
Before initiating treatment, confirm the rising titer with:
- Review of previous RPR/VDRL results to document the increase
- Confirmation with treponemal test if not already done
- Assessment of previous treatment history and adequacy
A fourfold or greater increase in nontreponemal test titers suggests treatment failure or reinfection 1.
Treatment Algorithm
Step 1: Determine Stage of Syphilis
- Early syphilis (primary, secondary, early latent <1 year)
- Late latent (>1 year) or unknown duration
Step 2: Administer Appropriate Penicillin Regimen
- For early syphilis: Benzathine penicillin G 2.4 million units IM as a single dose 1
- For late latent or unknown duration: Benzathine penicillin G 2.4 million units IM weekly for 3 consecutive weeks 1
Step 3: For Penicillin-Allergic Patients
- Penicillin is the only recommended treatment for pregnant patients
- Penicillin-allergic patients must undergo desensitization followed by appropriate penicillin treatment 1, 3
- Do not substitute alternative antibiotics during pregnancy
Special Considerations
First Dose Administration
For viable pregnancies, administer the first dose of benzathine penicillin G in a labor and delivery setting with:
- Continuous fetal monitoring for at least 24 hours
- Monitoring for Jarisch-Herxheimer reaction (occurs in up to 44% of pregnant women) 2
Jarisch-Herxheimer Reaction
This reaction can cause:
- Uterine contractions
- Fetal heart rate abnormalities
- Potential fetal compromise or stillbirth in severe cases 2
Treatment Adequacy
Research indicates that a single injection of benzathine penicillin G may be insufficient for pregnant women with syphilis. A study showed that treponemicidal coverage lasting 3 weeks or less resulted in:
- Decreased birth weight
- Increased risk of prematurity (RR 8.5)
- Higher perinatal mortality (RR 20.5) 4
Therefore, ensuring complete treatment with appropriate dosing is critical.
Follow-up Monitoring
After treatment:
- Monitor quantitative nontreponemal tests monthly during pregnancy 2
- A fourfold increase in titer indicates possible reinfection or treatment failure
- Perform ultrasound to assess for fetal syphilis if >20 weeks gestation (hepatomegaly, placentomegaly, elevated MCA peak systolic velocity, ascites, or hydrops fetalis) 2
- Continue monitoring after delivery at 3,6,9,12, and 24 months 1
Common Pitfalls to Avoid
- Do not use alternative antibiotics: Only penicillin effectively treats both maternal infection and prevents congenital syphilis
- Do not delay treatment: Each week of delay increases risk to the fetus
- Do not undertreat: Single-dose therapy may be insufficient for pregnant women, especially those with high initial titers (>1:16) 4
- Do not ignore partner treatment: Ensure all sexual partners are tested and treated to prevent reinfection
Remember that the rate of maternal titer decline is not tied to pregnancy outcomes, so monthly monitoring should focus on detecting any fourfold increase that would indicate reinfection or treatment failure 2.