Syphilis in Pregnancy — and How to Prevent Congenital Syphilis
Congenital syphilis is one of the most preventable but most damaging perinatal infections. Cases in the US have tripled in the last 5 years, almost entirely due to gaps in prenatal screening and access to treatment. The disease is fully curable in pregnancy — but only if it's caught and treated in time.
This guide covers what every pregnant person needs to know about syphilis testing, what happens if you test positive, and how treatment protects the baby.
The short answer
- All pregnant people should be tested for syphilis at the first prenatal visit
- High-risk people should be retested at 28 weeks and at delivery
- Penicillin G is the only effective treatment in pregnancy
- Treatment is highly effective if started early enough
- Earlier treatment = better outcomes — treatment in third trimester is less protective
- Congenital syphilis is devastating — stillbirth, early infant death, lifelong disability — and almost entirely preventable
- 2026 US epidemic: congenital syphilis cases have tripled; screening gaps are the main cause
Why this matters
Untreated maternal syphilis in pregnancy has catastrophic outcomes:
- 40% chance of stillbirth or perinatal death
- 70% of surviving infants show signs of congenital syphilis
- Long-term effects: deafness, vision loss, skeletal abnormalities, neurological damage, dental anomalies
With timely treatment: transmission rate drops below 5%, and most exposed babies are healthy.
The CDC's 2024–2026 reports show >3,800 congenital syphilis cases per year in the US — a level not seen since 1990s. The increase tracks the broader adult syphilis epidemic plus screening/treatment access gaps in high-risk populations.
Testing during pregnancy
First prenatal visit (universal)
Every pregnant person, regardless of risk profile, should be tested for syphilis at the first prenatal visit. CDC recommendation, ACOG recommendation, and universal practice in modern obstetrics.
Repeat testing
Test again at 28 weeks for:
- High-prevalence areas
- People with risk factors (multiple partners, history of STIs, substance use, sex work)
- Anyone with new symptoms
Test at delivery for:
- Anyone who hasn't had testing in pregnancy
- High-risk patients
- States that mandate it (many do)
What tests are used
Same as outside pregnancy:
- Non-treponemal (RPR or VDRL) — screening + treatment monitoring
- Treponemal (TPPA, FTA-ABS, EIA) — confirmation
See Syphilis test types compared for details on each.
Special consideration in pregnancy
False positives on non-treponemal tests are slightly more common in pregnancy (the immune changes of pregnancy can produce non-specific antibodies). This is why confirmation with treponemal testing is essential.
What if I test positive?
The same two-step confirmation algorithm applies:
- RPR positive + treponemal positive = syphilis confirmed
- RPR positive + treponemal negative = likely false positive (more common in pregnancy)
- Treponemal positive + RPR positive = same as #1
If confirmed, your provider will:
- Determine the stage of syphilis (primary, secondary, latent)
- Plan treatment immediately
- Schedule follow-up testing to monitor treatment success
- Coordinate with infectious disease specialist for complex cases
- Plan close fetal monitoring
Treatment in pregnancy
Penicillin G is the only effective treatment
This is critical. Other antibiotics may treat the maternal infection but do not adequately cross the placenta to treat the fetus.
- Doxycycline: contraindicated in pregnancy
- Azithromycin: crosses placenta but has high resistance rates and reduced efficacy
- Ceftriaxone: uncertain placental penetration
- Erythromycin: does not adequately cross placenta
Only penicillin G has reliable evidence for treating BOTH mother and fetus.
Treatment regimens (CDC, 2026)
Primary, secondary, or early latent syphilis
- Benzathine penicillin G 2.4 million units IM, single dose
- Some experts recommend a second dose 1 week later in pregnancy (controversial but increasingly common)
Late latent or syphilis of unknown duration
- Benzathine penicillin G 2.4 million units IM weekly × 3 doses
Tertiary or neurosyphilis
- Aqueous crystalline penicillin G IV — admission required
Penicillin allergy
If you have a true penicillin allergy: you must be desensitized so penicillin can be given safely. There is no acceptable alternative in pregnancy.
Desensitization is done in a hospital setting with cardiac monitoring, takes ~4–8 hours, and allows penicillin treatment to proceed safely. This is standard, widely available, and considered essential.
The Jarisch-Herxheimer reaction
A common reaction within hours of starting syphilis treatment: fever, chills, headache, muscle pain. Not an allergy — it's the immune response to killed bacteria releasing inflammatory products.
In pregnancy, this can cause:
- Preterm contractions
- Fetal heart rate changes
- Concern for fetal distress
For this reason, first dose of penicillin in pregnancy is often given in a monitored setting (L&D triage or hospital observation) with fetal monitoring.
The reaction usually resolves within 24 hours.
Monitoring treatment success
Maternal monitoring
- RPR titer at 1, 3, 6, 12 months after treatment
- Should drop 4-fold within 6–12 months
- If it doesn't drop or rises → retreatment needed
Fetal monitoring (post-treatment)
- Ultrasound for signs of fetal syphilis (hepatomegaly, ascites, hydrops)
- Serial growth scans
- Fetal heart monitoring in third trimester
What if treatment is in the third trimester?
Treatment late in pregnancy is less protective. The longer the fetus has been exposed, the higher the risk of damage already done. But treatment is still given because:
- It can prevent further progression
- It treats the mother
- It reduces transmission risk if not eliminating it
After third-trimester treatment, the infant is treated with penicillin as well, even if appears healthy.
What if treatment is missed?
If you reach delivery without treatment:
- Immediate testing at delivery (you and the infant)
- Infant treatment with penicillin (often a 10-day IV course) while testing is pending
- Mother treated with appropriate regimen
- Close follow-up for both
This is suboptimal but not catastrophic if caught at delivery.
Congenital syphilis — what it looks like
Most newborns with congenital syphilis are asymptomatic at birth. Symptoms develop over weeks to months.
Early congenital syphilis (under 2 years)
- Skin rash
- Hepatomegaly, splenomegaly
- Nasal discharge ("snuffles")
- Bone abnormalities
- Anemia
- Failure to thrive
Late congenital syphilis (over 2 years)
- "Hutchinson teeth" (notched incisors)
- Saddle nose deformity
- Vision changes (interstitial keratitis)
- Hearing loss
- Skeletal abnormalities ("saber shins")
- Neurodevelopmental delays
How is congenital syphilis prevented at the system level
- Universal prenatal screening at first visit
- Repeat screening in high-risk populations
- Rapid lab confirmation of positives
- Same-day or next-day treatment access
- Partner notification and treatment
- Affordable medication access (penicillin shortages have been a recurring issue)
Gaps in any of these = more congenital syphilis cases.
Partner treatment
If you have syphilis in pregnancy:
- Sexual partners in the prior 90 days (for early syphilis) must be tested and presumptively treated
- Continued partners during pregnancy need testing
- Partners should know the diagnosis (challenging emotional conversation, but medically essential)
Common patient concerns
"I was treated before pregnancy — am I safe?"
If you had a documented treatment and good RPR response, you're not at risk for transmitting to your baby. But retesting in pregnancy confirms.
"What if I get reinfected during pregnancy?"
Reinfection is possible. If your RPR titer rises during pregnancy, retreatment is needed.
"My partner won't get tested. What do I do?"
Continue your own treatment. Use condoms during pregnancy. Discuss with your provider about partner-notification services (anonymous notification through health departments is widely available).
"Will my baby need special care after birth?"
Newborns of mothers treated for syphilis in pregnancy are evaluated immediately after birth — typically:
- Physical exam
- Blood tests (RPR, treponemal, CBC)
- Sometimes lumbar puncture
- Long-bone X-rays
- Continued monitoring for 6–12 months
- Treatment with penicillin if any signs are concerning
"Can I breastfeed?"
Yes — syphilis is not transmitted through breast milk (unlike HIV in some scenarios). Active genital lesions could theoretically be a concern, but typical post-treatment scenarios are safe for breastfeeding.
"Will my next pregnancy be affected?"
No. Once successfully treated, syphilis does not cause transmission in future pregnancies. The treponemal test stays positive but that doesn't mean active infection.
When to seek immediate care
- Painless ulcer (chancre) in pregnancy — get tested same-day
- Diffuse body rash including palms and soles in pregnancy — secondary syphilis sign
- Unexplained fetal distress with maternal syphilis history — urgent OB evaluation
- Decreased fetal movement in someone diagnosed with syphilis
Resources
- CDC Congenital Syphilis Toolkit — clinical guidance + parent resources
- Local health department — syphilis is reportable; they often provide free testing/treatment
- Maternal Fetal Medicine (MFM) specialist — for complex cases or fetal involvement
Bottom line
Syphilis in pregnancy:
- Test at first prenatal visit, repeat at 28w + delivery if at risk
- Penicillin G is the ONLY treatment — desensitize if allergic
- Earlier treatment = better outcomes
- Untreated: 40% stillbirth risk, 70% of survivors affected
- Treated in time: transmission rate <5%, most babies healthy
- Congenital syphilis is preventable — gaps in care, not pathology, are the cause
- Monitor with serial RPR and ultrasound
Modern syphilis is fully curable. The tragedy of congenital syphilis is that it's a screening and access problem, not a treatment problem.
If you're pregnant and worried about syphilis: get tested today. If you're positive: penicillin treatment is the standard, safe, and highly effective. Treatment-in-time is the difference between a healthy baby and lifelong disability.
For more, see Syphilis symptoms by stage, Syphilis test types compared, Syphilis epidemic 2026, STI testing during pregnancy, and our Syphilis pillar guide.
