Congenital Syphilis Cases Continue to Rise Nationally

Cases of congenital syphilis—a form of syphilis passed from a pregnant woman to her baby—have risen sharply for more than a decade. Public health experts are sounding the alarm about this preventable disease that can be deadly to babies if not promptly detected and treated.

In 2012, there were only 335 cases of congenital syphilis, a sexually transmitted infection (STI), according to the Centers for Disease Control and Prevention (CDC). Last year, that number rose to nearly 4,000, underscoring an urgent public health challenge.

Syphilis is a bacterial infection that typically spreads through sexual contact. It develops in stages, each with its own symptoms. In the early stages—primary and secondary syphilis—there may be a painful sore, rashes, or flu-like symptoms. After that, the infection can go into a latent stage, meaning it’s still in the body but causes no obvious symptoms. If it isn’t treated, syphilis can eventually reach a tertiary stage, which can cause serious damage to the heart, brain, blood vessels, and other organs. In rare cases, without proper treatment it can even lead to death.

Congenital syphilis occurs when an untreated pregnant woman passes the infection to her baby during pregnancy or at birth. It can cause miscarriage, stillbirth, prematurity, low birth weight, and death shortly after birth. Babies born with congenital syphilis can have deformed bones, enlarged liver, enlarged spleen, jaundice (yellowing of the skin, the whites of the eyes, and mucous membranes), anemia (low red blood cell count), thrombocytopenia (low platelet count), wart-like lesions, peeling skin on hands or feet, and rash on the neck, arms, and mouth.

Infants with congenital syphilis may have a persistently runny nose that starts within one week of birth, with drainage that can contain blood or look white. As many as six in 10 newborns with congenital syphilis have neurosyphilis, a complication that occurs when the infection spreads to the central nervous system; this can lead to stroke, seizures, and eye problems such as cataracts.

“We start with a blood test, just like we do in adults,” says Thomas Murray, MD, PhD, a Yale Medicine pediatric infectious diseases specialist. “If this is concerning, we do other tests. We want to make sure the infection hasn’t invaded the brain or nervous system so we will do a spinal tap to check.”

The syphilis blood test for newborns is compared with the mother’s test results, with a second test to confirm the diagnosis is correct. If this information points toward the baby having syphilis, or if the mother had it and wasn’t adequately treated during pregnancy with an antibiotic, additional testing may follow. This may include X-rays to check for bone changes, further blood tests to monitor liver function and blood counts, an eye exam, and, depending on the baby’s age, a spinal tap to look for syphilis in the spinal fluid.

Early diagnosis is key. Some infected infants show no symptoms at birth, but if the baby has the infection and does not receive treatment, serious complications can occur. Usually, they start in the first few weeks after birth, but it can be years later that problems emerge.

Syphilis can be prevented by practicing safe sex, including using condoms consistently and correctly and being in a mutually monogamous relationship with a partner who has been tested for the STI.

The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be screened for syphilis at their first prenatal care visit, followed by rescreening during the third trimester and at delivery.

A baby cannot develop congenital syphilis if the mother is not infected. The infection is treated with the antibiotic penicillin, which is highly effective for both adults and newborns. If the mother receives appropriate treatment during pregnancy, the chance the baby will be infected is significantly reduced. Newborns with congenital syphilis usually receive intravenous penicillin for 10 days, though in some cases, such as when there has been possible exposure but infection is unclear, a single-dose injection is given.

“The earlier we catch it, like with other infections, the better the infant will do,” Dr. Murray says.

“The reason we are seeing a sharp increase in congenital syphilis is because there’s an increase in rates of syphilis in women of childbearing age,” Dr. Murray says.

Between 2016 and 2020, the rate of primary and secondary syphilis in women more than doubled in the U.S., and during that same time period, the national congenital syphilis rate increased by more than 20%, according to the CDC. However, the most recent report from the agency, which has not yet been finalized, reveals that the rate of primary and secondary syphilis in women slightly declined between 2023 and 2024—but congenital syphilis remains high.

Experts also connect the rise in congenital syphilis to inadequate prenatal care, which may stem from housing insecurity, mental health challenges, and substance use. Two in five infants with congenital syphilis were born to women who did not receive any prenatal care, according to the CDC.

“If a woman is not seen routinely throughout her pregnancy, these tests may not be done and syphilis won’t be picked up until delivery, and at that time, the baby has increased risk,” Dr. Murray says. “Women of childbearing age who are thinking of becoming pregnant should be screened. If we can successfully treat syphilis before pregnancy, there’s no risk to the baby, as long as reinfection doesn’t occur.”

Like with all STIs, if someone has syphilis, it’s important to notify sexual partners to prevent the further spread of infection.

“Treatment for syphilis is effective, but it does not prevent reinfection. If you’re treated and you have a partner who is infected and you continue to have intimate relations with that partner, you can become reinfected,” Dr. Murray says.

Monitoring community infection trends—and ensuring that people at risk are tested and treated—is critical. “A baby with congenital syphilis can be very, very sick, and it’s all preventable,” Dr. Murray says.