Congenital syphilis occurs when a pregnant person infected with the organism responsible for syphilis (Treponema pallidum) transmits that infection to the fetus via the placenta. Congenital syphilis may be contracted at any stage of maternal infection, at any time during pregnancy, or via contact with maternal lesions at the time of delivery.

Recently, the Centers for Disease Control and Prevention reported a tenfold increase in congenital syphilis in the past 10 years. In the United States, cases have increased by 755% during the past decade, with 335 known cases in 2012 and 2,865 cases in 2021. “We haven’t seen these high rates since the early 1990s,” says pediatric infectious diseases expert Kari Neemann, MD. “Since 2017 in Nebraska, we’ve seen a 373% overall increase in syphilis, a 1,163% increase among females, and a 1,100% increase in congenital syphilis.”

Why are congenital syphilis rates increasing?

“There are likely many reasons, and while I would like to blame the pandemic period, these increasing trends have been present now for more than 20 years,” says Dr. Neemann. “When we look at the adults experiencing primary and secondary syphilis, there has been a substantial increase in the proportion occurring in individuals participating in heterosexual activities and women overall. We also know that ethnic disparities exist.”

As the rates of syphilis increase in women of childbearing age, we will undoubtedly continue to see rates of congenital syphilis rise. To help combat this trend, all pregnancies must be tested at the first prenatal visit so that timely treatment can be given.  The risk for new infection should be assessed throughout pregnancy. 

How does syphilis affect pregnancy?

Syphilis can be devastating to pregnancy. Untreated early syphilis results in up to 40% of pregnancies experiencing spontaneous abortion, stillbirth, or early infant death. During this period, there is a high chance of passing the infection to the fetus (60% to 100%). The risk of transmission also increases the further along the pregnant person is in their pregnancy. This risk decreases the farther the pregnant individual is from the initial infection (early latent stage 40%, late latent stage under 8%).

How does congenital syphilis affect newborns?

Newborn symptoms are most affected by the timing of maternal infection and subsequent treatment. Overall, 60% to 90% of infants with congenital infection will be born without any apparent symptoms.

Left untreated, however, infants who don’t have symptoms at birth can develop into late manifestations, including blindness, deafness, abnormal teeth development, developmental delay, or skeletal abnormalities. 

When symptoms are present, the most common findings include nasal discharge, a rash that might consist of spots on the palms and soles (present at birth or develop over the first few weeks if untreated), the liver or spleen may be enlarged, possible jaundice, enlarged lymph nodes, or skeletal or eye abnormalities. The infant’s blood count may show decreases in different cell lines, and liver function may be affected.

How is acquired syphilis infection spread?

Acquired syphilis (not congenital) is almost always transmitted through direct sexual contact with someone infected. “As the initial symptoms of both primary and secondary syphilis will resolve with time and may not be recognized by the infected individual, I would encourage all sexually active adults to discuss syphilis testing with their health care provider, especially if they have had a new partner,” says Dr. Neemann.

Acquired syphilis can be divided into three stages: 

1. Primary syphilis usually presents as a painless, thickened ulcer on the skin or mucous membrane at the transmission site. The lesions appear about three weeks after exposure and will heal spontaneously in a few weeks. 
2. Secondary syphilis occurs if the primary-stage infection is not treated. It can travel throughout the body, causing symptoms such as fever, sore throat, swollen lymph nodes, or a characteristic rash that includes the palms and soles. This stage will resolve independently in 3 to 12 weeks even if not treated, but the infection continues.
3. Latent syphilis begins when you no longer have any clinical disease symptoms. Less than a year from the initial infection is the early latent stage, and over a year from the initial infection is the late latent stage.

Tertiary syphilis occurs 15 to 30 years after a nontreated infection. It can manifest with noncancerous tissue growths, cardiovascular symptoms, and central nervous system problems like hearing loss, dementia, eye inflammation and more. 

Screen for congenital syphilis at the first prenatal visit

“Being tested or retested for syphilis in pregnancy is not intended to be a judgment on the pregnant individual’s character; it is done truly to ensure that both mother and infant have a good outcome,” adds Dr. Neemann. “I would encourage every pregnant woman to discuss this testing with their health care provider. No infant should leave the hospital unless the mother has been tested for syphilis at least once during pregnancy.” 

Screening involves a blood test that looks to see if your immune system has been in contact with the organism that causes syphilis. Repeat screening is recommended at 28 to 32 weeks and at delivery for individuals who may be at higher risk of acquiring syphilis during pregnancy. Additionally, those who experience stillbirth after 20 weeks should be tested for syphilis.

Does treatment during pregnancy prevent congenital syphilis?

Antibiotic therapy during pregnancy can treat both the pregnant individual and the infant. The preferred treatment for pregnant individuals is a penicillin injection, with the number of injections based on the stage of syphilis.

“That said, antibiotics cannot treat any damage already inflicted onto the developing fetus but hopefully prevent any subsequent damage,” says Dr. Neemann. “This is why it is important to diagnose syphilis early in pregnancy and to take steps to prevent acquisition throughout pregnancy.” 

Treatment for infants born with congenital syphilis

Infants born with congenital infection are treated with penicillin intravenously for 10 days. This treatment will cure the infant but doesn’t repair any damage that may have already occurred secondary to the infection. These infants will not go on to develop the late findings of congenital syphilis.