In 2016, 628 cases of congenital syphilis were reported—the highest rate since 1998.
If a pregnant woman has the infection and it goes untreated, her baby can be born dead, deaf or blind, or with nerve damage or bone deformities, according to the U.S. Centers for Disease Control and Prevention.
The increase in congenital syphilis came after syphilis cases rose among women, the agency said.
Experts have long advised syphilis screening for all pregnant women, ideally at their first prenatal care visit. If a woman has the infection, antibiotic treatment is very effective at preventing newborn syphilis.
"It's easily detected, and it's easily treated," said Dr. Chien-Wen Tseng, an associate professor at the University of Hawaii School of Medicine. "So there's really no reason that rates of congenital syphilis should be going up."
Tseng is a member of a U.S. Preventive Services Task Force panel that is issuing new recommendations on prenatal syphilis screening. The task force is an independent panel of medical experts, funded by the U.S. government, that reviews research evidence and makes recommendations on preventive health care.
There is nothing new in the latest recommendations: They reaffirm the task force's 2009 advice, that all pregnant women be screened for syphilis.
But now there is even more urgency to get the word out, Tseng said.
Syphilis cases, overall, have been on the rise for years. According to the CDC, there were nearly 9 cases per 100,000 Americans in 2016—the highest rate since 1993. The majority of those infections were among gay men, but the rate among women has been increasing, too.
Syphilis often causes no noticeable symptoms, and even when it does, those symptoms may be vague—a non-itchy skin rash and swollen lymph nodes, for instance.
Research shows that the earlier a pregnant woman is treated for syphilis, the better. But, Tseng said, studies also show that many women are either not screened at all, or screened too late: 20 percent are screened only at the time of delivery, the task force report said.
Many people—even doctors—think of syphilis as a thing of the past, said Dr. Sarah Kidd, of the CDC's division of STD prevention.
"Providers need to be aware that syphilis is not as rare as it used to be," said Kidd, who was not involved in the task force recommendations.
The recommendations say only that all pregnant women should be screened—and do not address the question of how often.
But, Kidd said, the CDC suggests that women at high risk of syphilis be screened multiple times: at the first prenatal visit, at the beginning of the third trimester, and at delivery.
That includes women with a history of syphilis, drug use or incarceration; women with multiple sex partners; and those who live in areas with a high prevalence of the infection.
According to Tseng, the message for women is straightforward: "Get prenatal care as early as you can," she said.
Kidd agreed. "This is a good reminder of the importance of early prenatal care."
More broadly, it's also critical to prevent, detect and treat syphilis in general, according to Fred Wyand, director of communications for the American Sexual Health Association.
Poverty and other social factors have a big impact on rates of syphilis and other sexually transmitted diseases among women, Wyand noted.
"This has been exacerbated," he said, "by funding cuts to health departments across the U.S. that erode their ability to detect and treat diseases like syphilis—which, of course, is crucial to breaking the disease cycle."