Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. Routine prenatal screening for syphilis is a mandatory standard of care in modern obstetrics. This universal testing is implemented because an untreated infection in a pregnant person poses an extreme and preventable threat to the developing fetus. Screening is performed early in pregnancy to allow for immediate intervention before the bacteria can cause irreversible harm. This practice of early detection and treatment is a highly effective public health measure designed to protect the infant’s health.
The Specific Risks of Untreated Syphilis During Pregnancy
Untreated syphilis leads to severe consequences for the fetus, collectively referred to as adverse pregnancy outcomes. The bacteria can cross the placental barrier, typically after the first trimester, causing congenital syphilis. This transmission is highly likely, with infection rates approaching 100% when maternal syphilis is untreated.
The outcomes of congenital syphilis are devastating, ranging from early fetal loss to long-term health issues. Untreated maternal infection is associated with a high risk of miscarriage, stillbirth, and neonatal death, accounting for up to 40% of cases. Infants who survive may be born prematurely or with a low birth weight.
The infection can impact nearly every organ system. Surviving infants may present with symptoms such as bone deformities, severe anemia, liver and spleen enlargement, and jaundice. Long-term consequences include neurological damage, developmental delays, seizures, and permanent sensory impairments like blindness or deafness. Immediate treatment following a positive maternal test is the only safe course of action, as many infected babies appear healthy at birth.
How and When Syphilis Screening Occurs
Syphilis screening during pregnancy is a simple, non-invasive blood test. Public health organizations mandate this testing for all pregnant individuals at their first prenatal care visit, usually in the first trimester. This early screening ensures that necessary treatment can be administered quickly to prevent fetal infection.
The testing typically follows a two-step diagnostic process to maximize accuracy. The initial step uses a non-treponemal test (e.g., RPR or VDRL) which screens for antibodies produced in response to tissue damage. If the initial screen is reactive, a second, treponemal-specific test confirms the presence of antibodies specific to Treponema pallidum. This two-step approach helps distinguish a true infection from a false-positive result.
Repeat testing is recommended for high-risk individuals because the risk of acquiring syphilis continues throughout pregnancy. High-risk factors include living in areas with high syphilis prevalence, having a history of other STIs, or having new sexual partners during pregnancy. For these individuals, retesting is advised early in the third trimester (around 28 weeks) and again at delivery. This repeated screening safeguards against a late-stage infection that could harm the newborn.
Effective Treatment and Prevention of Congenital Syphilis
The primary reason for universal prenatal screening is that syphilis is curable, and timely treatment is highly effective at preventing congenital syphilis. Treatment for both the pregnant person and the fetus relies on a single medication: Penicillin G. Penicillin G is the only drug proven to cross the placenta consistently, reaching the fetus to treat any existing infection.
The effectiveness of this treatment is high, approaching 100% when administered appropriately. The success rate in preventing congenital syphilis has been documented to be as high as 98.2% across all stages of maternal infection. Early intervention is paramount, as the earlier Penicillin G is given, the lower the risk of adverse outcomes for the baby.
For individuals with a penicillin allergy, a desensitization process is performed to safely allow them to receive Penicillin G, since alternative antibiotics are not proven to effectively prevent congenital syphilis. Following treatment, the patient’s antibody levels are monitored via repeat blood tests to ensure the infection is clearing and the treatment was successful. This simple regimen transforms a highly dangerous prenatal infection into a manageable and preventable condition.