Congenital Syphilis: How It Harms Babies, and How Testing in Pregnancy Prevents It

Congenital syphilis (CS) happens when syphilis passes from a pregnant person to the baby. Syphilis is a common, curable sexually transmitted infection (STI) that anyone who is sexually active can get — and left untreated, it causes serious harm.

The one thing to do: get tested — and treated if needed — during pregnancy. If you don't have syphilis, your baby can't get CS.

Image from CDC's page on congenital syphilis

A fast-growing problem

CS cases have more than tripled in recent years. Nearly 4,000 were reported in 2024 alone — the most in a single year since 1994.

What it can do to a baby

How badly CS affects a baby depends on how long the parent had syphilis and whether, and when, it was treated.

A baby can have CS and look healthy at birth. Without prompt treatment, problems usually appear in the first few weeks — but can emerge years later. Untreated babies who develop symptoms can die, or have developmental delays or seizures.

Protecting your baby

1. Get tested at your first prenatal visit

Ask about a syphilis test the first time you see a provider in pregnancy — even if you've been tested before. Tell them about:

• any new or unusual symptoms;
• any drugs or medicines you use;
• whether you have new or multiple sex partners;
• your risk, such as how common syphilis is where you live.

That helps them decide on testing. Some people should be tested again at the start of the third trimester and at delivery.

You can have syphilis and not know it — it may cause no symptoms, very mild ones, or symptoms that look like other illnesses.

If you test positive:

• get treated right away — syphilis is curable with the right antibiotics;
• make sure your sex partner(s) are treated too;
• go back for follow-up testing to confirm the treatment worked.

Having had syphilis doesn't protect you — you can catch it again after treatment, so keep lowering your risk.

2. Lower your risk before and during pregnancy

Preventing syphilis in sexually active people is the best way to prevent CS. The only sure way to avoid STIs is not having vaginal, anal or oral sex. Otherwise:

• be in a long-term, mutually monogamous relationship with a partner who has tested negative;
• use condoms correctly every time. They block contact with a sore — but sores can appear where a condom doesn't cover, and contact with those can still spread syphilis.

If you're sexually active, talk openly with your provider and ask whether you should be tested for syphilis and other STIs.

Diagnosing CS in a newborn

Your provider weighs several things: your syphilis test results, and whether you were treated during pregnancy if you had syphilis. They may also test the baby's blood, do a physical exam, or order tests such as a spinal tap or x-ray. CDC gives providers specific guidance on evaluating babies born to people who tested positive in pregnancy.

Treatment for babies

CS is treatable — and babies need treatment right away. Depending on the evaluation, a baby may need 10 days of antibiotics in hospital, or sometimes a single injection. Follow-up care checks that the treatment worked.

Sources

Based on "About Congenital Syphilis," Centers for Disease Control and Prevention; a work of the United States government in the public domain.