Congenital syphilis

What is congenital syphilis?

Congenital syphilis is when a baby is born with syphilis, passed from the birthing parent during pregnancy or birth. Most cases happen during pregnancy, but it can also occur during vaginal birth if the baby comes into direct contact with a syphilis sore.

Syphilis is a sexually transmitted infection (STI also called STD) that spreads through unprotected sex or direct contact with a syphilis sore. If you have syphilis during pregnancy and don’t get treated, you can pass it to your baby. If left untreated, syphilis can cause serious problems for the baby, including stillbirth and infant death. Nearly 9 in 10 cases (90 percent) of congenital syphilis in the United States are linked to delayed testing or not getting proper treatment in time.

How can congenital syphilis affect your baby?

Congenital syphilis can cause problems during pregnancy and after birth. Some babies may look healthy at birth but develop issues later if not treated quickly. Complications depend on how long you were infected with syphilis during pregnancy and if and when you got treatment.  

During pregnancy, congenital syphilis may cause:

• Miscarriage. Loss of the baby before 20 weeks of pregnancy.
• Preterm birth. Birth before 37 weeks of pregnancy.
• Fetal growth restriction (also called growth-restricted, small for gestational age or small for date) and low birthweight. Babies may be smaller than expected or weigh less than 5 pounds, 8 ounces.
• Problems with the placenta and the umbilical cord. An enlarged placenta or swollen umbilical cord can prevent them from working properly to support the baby in the womb.
• Stillbirth. Loss of the baby after 20 weeks of pregnancy.

After birth, congenital syphilis may cause:

• Neonatal death. Death within the first 28 days of life.
• Fever, jaundice, or liver and spleen swelling: This includes yellowing of the skin and eyes (jaundice) and swelling of the liver and spleen (hepatosplenomegaly).
• Anemia. This is when your baby has a shortage of healthy red blood cells.
• Rashes, runny nose, and meningitis: These can appear on the skin or in the nervous system.

Long-term problems if untreated include:

• Bone and joint issues (e.g., curved shinbones, flat nose, widely spaced teeth).
• Vision or hearing problems.
• Nervous system damage (e.g., weak arms or legs, seizures).
• Delays in reaching milestones like sitting, walking, or talking.

How is congenital syphilis diagnosed in your baby?

During prenatal visits, healthcare providers check for syphilis with blood tests. If syphilis is detected, the provider will check the baby after birth using:

• Blood tests
• Physical and eye exams
• Imaging tests, like X-rays or ultrasounds
• A spinal tap to test fluid from around the brain and spine

How is congenital syphilis treated?

Babies with congenital syphilis are treated with penicillin, an antibiotic given as a shot or through an IV. Early treatment can cure the infection and lower the chance of long-term problems. Follow-up care is important to make sure the treatment is working.

The amount of treatment your baby gets depends on the infection and condition. For some babies, congenital syphilis can be completely cured. For others, they may need treatment for health conditions caused by the infection. If your baby has congenital syphilis, it’s important to get treatment right away to help prevent complications. Take your baby to all medical checkups to make sure the treatment is working.

Can you prevent your baby from having congenital syphilis?

Congenital syphilis is preventable. Protect yourself and your baby from infection by taking these steps:

• Practice safe sex: Use condoms or dental dams and have sex with only one person. Your partner should be free of an STI.
• Go to all prenatal care visits: Regular checkups help identify and address risks, including syphilis. If you’re at risk for syphilis, your provider gives you a blood test to see if you have the infection.
• Get tested and treated: If you think you may have syphilis, tell your provider right away. The sooner you’re treated, the less likely you and your baby are to have complications from your infection.
• Ask your partner to get tested and treated: If you get treated for syphilis, you’re no longer infected. But if your partner is infected, you can get infected again. Prevent reinfection by encouraging your partner to get tested and treated.

More information:

Protect your baby from syphilis (infographic)

CDC congenital syphilis fact sheet

Last reviewed: January, 2025