Congenital syphilis is a serious infection passed from a pregnant person to their baby, either during pregnancy or at birth. It happens when the bacterium that causes syphilis crosses the placenta and enters the baby’s bloodstream directly, spreading quickly to organs including the liver, kidneys, spleen, bones, and heart. Cases in the United States have risen roughly 700% since 2015, with nearly 4,000 reported in 2024 alone.
How the Infection Passes to the Baby
The syphilis bacterium crosses the placental barrier easily, meaning a fetus can become infected at any point during pregnancy. Transmission happens most often during the third trimester, but infections acquired earlier tend to cause the worst outcomes. When the bacterium reaches the fetus during the first trimester, the risk of miscarriage, stillbirth, premature birth, and death around the time of delivery is significantly higher.
A large meta-analysis found that 26% of pregnancies with untreated syphilis end in stillbirth or fetal loss, compared to about 4% in uninfected pregnancies. Even when treatment begins by the third trimester, that rate only drops to around 21%, which is why early screening matters so much. When infection occurs later in pregnancy, many babies are born appearing completely healthy, with no visible signs at birth. That doesn’t mean they’re unaffected. Without treatment, problems can develop weeks, months, or even years later.
Signs in Newborns and Infants
Symptoms that appear within the first two years of life are classified as “early” congenital syphilis. Many infected newborns look healthy at delivery, which is part of what makes this condition so dangerous. When symptoms do appear, they can include:
- Enlarged liver and spleen, sometimes visible as a swollen belly
- Severe anemia
- Jaundice (yellowing of the skin and eyes)
- Skin rashes
- Bone deformities
- Brain and nerve problems, including blindness, deafness, or meningitis
A distinctive early sign is persistent nasal discharge, sometimes called “snuffles,” which is highly contagious. Rashes often appear on the palms and soles. Because these symptoms overlap with other newborn conditions, blood testing is essential for a definitive diagnosis.
Long-Term Effects in Untreated Children
When congenital syphilis goes untreated past the age of two, it can cause permanent damage known as “late” congenital syphilis. The infection produces tissue destruction that tends to target the nose, the roof of the mouth, and the nasal septum, sometimes causing visible disfigurement. Bone changes include bowing of the shins (called saber shins) and prominent bossing of the forehead.
A cluster of three specific problems, known as the Hutchinson triad, is considered diagnostic of late congenital syphilis: inflammation of the cornea that can lead to scarring and vision loss, notched and widely spaced upper front teeth (Hutchinson incisors), and progressive hearing loss from nerve damage. Hearing loss can appear at any age and often worsens over time. Some children also develop intellectual disability or vision problems progressing to blindness. Cracks and scarring around the mouth, called rhagades, and abnormal development of the upper jaw are less common but characteristic features.
Why Cases Keep Rising
The CDC reported that U.S. cases of congenital syphilis increased for the 12th consecutive year in 2024. In 2015, just 495 cases were reported nationwide. By 2024, that number had climbed to nearly 4,000. The surge reflects rising syphilis rates in the general population, gaps in prenatal care, and missed opportunities for screening during pregnancy.
A key factor is timing. Syphilis is straightforward to treat during pregnancy, but only if it’s detected. Some pregnant people don’t receive prenatal care early enough, or at all. Others are tested once early in pregnancy but acquire the infection later and aren’t retested. In areas where syphilis rates are high, a negative test in the first trimester doesn’t guarantee the person remains uninfected through delivery.
Screening During Pregnancy
The U.S. Preventive Services Task Force recommends universal syphilis screening as early in pregnancy as possible, ideally at the first prenatal visit. If early screening wasn’t done for any reason, testing should happen at the first available opportunity, even if that means testing at the time of delivery.
The American College of Obstetricians and Gynecologists recommends rescreening all pregnant people again in the third trimester and at birth. The CDC takes a similar approach for those at higher risk, recommending repeat testing at 28 weeks and again at delivery. A simple blood test is all that’s needed. Because syphilis in its early stages often produces no noticeable symptoms, screening is the only reliable way to catch it before it reaches the baby.
Treatment and Outlook
Penicillin is the standard treatment for congenital syphilis and has been for decades. Infected newborns typically receive intravenous penicillin for 10 days. The earlier treatment begins, the better the outcomes. When syphilis is caught and treated during pregnancy, especially before the third trimester, the risk of serious complications for the baby drops dramatically.
Babies who are treated early and have no signs of organ damage generally do well. Those diagnosed later, particularly after symptoms have already developed, may face lasting effects depending on which organs were affected. Hearing loss and vision problems, once established, are not always reversible. Bone and dental changes from late congenital syphilis are permanent. This is why prevention through prenatal screening remains far more effective than treatment after birth. Every case of congenital syphilis represents a missed opportunity, because the tools to prevent it are simple, inexpensive, and widely available.