Congenital syphilis is a serious infection that passes from a pregnant person to their baby, either through the placenta during pregnancy or through contact with an infected sore during delivery. It is entirely preventable with early testing and treatment, yet cases in the United States have risen 700% over the past decade, reaching nearly 4,000 reported cases in 2024.
How the Infection Passes to the Baby
The bacterium that causes syphilis can cross the placenta and enter the baby’s bloodstream at any point during pregnancy. Unlike adult syphilis, where the bacteria first infect the skin and then slowly spread, in a fetus the bacteria go directly into the blood and rapidly reach most major organs, including the liver, spleen, kidneys, bones, and heart. This causes widespread inflammation across multiple organ systems at once.
The risk of transmission depends heavily on the stage of the mother’s infection. During primary or secondary syphilis, when symptoms like sores or rashes are active, the transmission rate ranges from 60% to 100%. During early latent syphilis (when symptoms have disappeared but the infection is relatively recent), the rate drops to around 40%. In late latent syphilis, the risk falls below 8%. The placenta itself often becomes visibly enlarged due to the inflammatory response, which can be one of the earliest signs something is wrong.
Signs in Newborns and Young Infants
Many babies with congenital syphilis appear healthy at birth, which makes the condition easy to miss without proper testing. When symptoms do appear in the first two years of life, they can include an enlarged liver and spleen (the single most common finding), severe anemia, jaundice, skin rashes, and deformed bones. Some infants develop meningitis or nerve damage that leads to blindness or deafness. The range of possible problems is wide because the bacteria have already spread throughout the body before birth.
Even babies who look completely normal at delivery can have underlying neurological issues. One study using standardized neurological exams found that all 11 newborns tested after treatment for congenital syphilis scored in the suboptimal or abnormal range, and about 73% showed abnormal general movement patterns. Follow-up research suggests these neurological differences can persist through at least the first year of life, raising concerns about longer-term developmental effects.
Late Congenital Syphilis
If the infection goes untreated or is only partially treated, a second wave of problems can emerge later in childhood, typically after age two. These are sometimes called the “stigmata” of congenital syphilis because they leave permanent physical markers. The classic combination, known as Hutchinson’s triad, includes three features: notched, peg-shaped permanent upper front teeth; inflammation of the cornea (interstitial keratitis) that can impair vision; and nerve-related deafness.
Other late signs include a flattened “saddle” nose caused by destruction of the nasal septum, a prominent forehead sometimes called an “Olympian brow,” forward bowing of the shinbones (saber shins), and joint swelling. Some children develop neurological conditions similar to those seen in adults with advanced untreated syphilis, affecting the brain and spinal cord. These complications are largely irreversible, which is why early detection matters so much.
How It’s Treated
Penicillin given intravenously is the standard treatment for infected newborns, typically administered over a 10-day course in the hospital. The earlier treatment begins, the better the outcomes. When syphilis is caught and treated in the mother during pregnancy, transmission to the baby can be prevented entirely. This is what makes the rising case numbers so frustrating to public health experts: the tools to stop congenital syphilis exist and are straightforward.
Why Cases Keep Rising
The surge in congenital syphilis is closely tied to rising syphilis rates in the general population, which roughly tripled between 2018 and 2022. But the more immediate driver is a gap in prenatal care. A CDC investigation in Clark County, Nevada found that fewer than half of mothers who delivered a baby with congenital syphilis had received any prenatal care during their pregnancy. Among those who did get tested but lacked regular prenatal visits, about 70% weren’t tested until fewer than 45 days before delivery, far too late for treatment to protect the baby.
Nationally, lack of timely testing and inadequate treatment during pregnancy contributed to 88% of congenital syphilis cases reported in 2022. The problem isn’t a lack of knowledge about what works. It’s a failure to connect pregnant people with care early enough. Barriers include limited access to healthcare, substance use, housing instability, and gaps in the healthcare system itself.
Prenatal Screening Requirements
Most U.S. states now require syphilis testing at the first prenatal visit. Many also mandate a second test during the third trimester, typically between 28 and 32 weeks, and some require testing again at delivery. States with higher syphilis rates tend to have more aggressive screening laws. Georgia, for example, requires testing at the first visit, at 28 to 32 weeks, and at delivery for all pregnancies. Other states reserve delivery testing for people living in areas with high syphilis rates or those with specific risk factors.
The three-test approach exists because a person can acquire syphilis at any point during pregnancy. A negative result at the first visit doesn’t guarantee the baby is safe if the mother is exposed later. Repeat testing catches infections acquired mid-pregnancy, leaving enough time for treatment to prevent transmission.