Ana was 24 years old and 18 weeks pregnant when the result arrived. She had felt almost nothing, the antenatal appointments had shown no signs of alarm, and the pregnancy seemed as peaceful as every expectant mother hopes for. But the VDRL came back positive, with a titre of 1:32, and everything changed. The diagnosis was active syphilis. With no previous treatment, no treated partner, with almost five months of pregnancy, she and her baby were in real danger, and time was already running out for both of them.

Stories like Ana's repeat thousands of times every year in Brazil. Congenital syphilis, the kind that passes from mother to child within the womb, remains one of the most frequent and, at the same time, most preventable causes of death and serious complications in newborns in the country. Preventable because all it takes is a simple test and an accessible antibiotic for it to never happen.

How the Bacterium Reaches the Baby

Syphilis is caused by a bacterium called Treponema pallidum, transmitted mainly through unprotected sexual contact. When a pregnant woman is infected, this bacterium can cross the placenta and reach the foetus at any stage of pregnancy, but especially from the second trimester onwards, when the placenta becomes more permeable to what circulates in the mother's blood.

Here is the frightening point: the more recent the infection, the more bacteria are circulating actively and the greater the chance of the baby being contaminated. In cases of untreated primary or secondary syphilis, this risk can exceed 80%. It is not a vague estimate. It is a number that should be talked about more.

What Happens to the Mother

Part of the problem is that syphilis rarely gives clear signs.

In the primary phase, a painless sore appears in the genital area, known as a hard chancre, which disappears on its own in a few weeks and gives the woman the impression that it has passed.

In the secondary phase, the infection spreads throughout the body and can cause:

  • Red patches on the skin (including on the palms of the hands and soles of the feet, a characteristic feature of the disease)
  • Low-grade fever
  • Malaise
  • Enlarged lymph nodes

After that comes the latent phase: with no visible symptoms, but with the bacterium still alive and present.

It is exactly in this silent phase that many women arrive at antenatal appointments without knowing what they are carrying. And it is in this phase that the baby is at greatest risk, because the infection follows its course within the womb without anyone noticing.

The Consequences for the Baby

When syphilis is not treated during pregnancy, the consequences for the baby can be extremely serious. The baby may be stillborn, born prematurely, with very low birth weight, or apparently healthy, but carrying complications that will only appear months or years later. There is no single outcome: the disease has many ways of causing damage.

Early and Late Congenital Syphilis: Two Distinct Scenarios

When signs appear in the first two years of life, this is called early congenital syphilis. The baby may present with:

  • Stuffy nose with persistent discharge
  • Patches or blisters on the skin
  • Swollen belly due to enlarged liver and spleen
  • Jaundice
  • Anaemia
  • Bone pain that prevents him or her from moving arms and legs freely

Often, the baby cries inconsolably when touched, simply because they are in pain, and this is frequently confused with colic or temperament.

When the diagnosis is delayed even further, the disease enters its late phase, after two years of life, and the condition becomes much more difficult to reverse. Complications include:

  • Permanent deafness
  • Blindness from eye inflammation
  • Sunken nose in the middle of the face in a saddle shape
  • Malformed teeth and bones
  • Neurological impairment that stays with the child forever

These are complications that a simple penicillin injection during antenatal care would have prevented.

Diagnosis: Understanding the Tests

The test that screens for syphilis is called the VDRL, and it works by measuring the inflammatory reaction that the body produces in response to the infection. The result comes in the form of a titre, which is simply a sequence of blood dilutions: 1:2, 1:4, 1:8, 1:16, 1:32 and so on. The higher the number, the more intense the infection at that moment. A titre of 1:32 indicates much more bacterial activity than one of 1:4, for example.

But the VDRL alone does not confirm the diagnosis. To confirm that it is really syphilis, a second test is needed, called a treponemal test, such as the FTA-Abs or CLIA, which identifies specific antibodies against the bacterium. The two together form the complete diagnosis.

The Brazilian protocol recommends that this screening be done at three moments:

  1. In the first trimester of pregnancy
  2. In the third trimester
  3. At the moment of delivery

Any abnormal result requires immediate investigation and treatment.

Treatment in Pregnancy: Why Penicillin is Irreplaceable

There is no safe alternative to penicillin for treating syphilis in pregnancy. Other antibiotics work outside of pregnancy, but they do not cross the placenta effectively enough to protect the baby. For pregnant women with confirmed penicillin allergy, the protocol includes a desensitisation process in a hospital setting before starting treatment. There is no shortcut in this case.

The form, dose and duration of treatment depend directly on the stage at which the infection is found, and this is where the VDRL titre comes in as an essential clinical guide.

Benzathine Penicillin

In more recent forms, such as primary, secondary and early latent syphilis with less than one year of evolution, a single dose of benzathine penicillin of 2.4 million units, given as an intramuscular injection divided between both buttocks, is already sufficient. Benzathine is a slow-release version of the antibiotic: it enters the body gradually over days, which is exactly what is needed when the infection is still in an early stage.

When the infection is older, with more than one year of evolution or with unknown duration, treatment needs to be longer:

  • Three weekly doses of benzathine penicillin
  • One dose per week for three consecutive weeks
  • Totalling 7.2 million units

The detail matters: if the interval between doses exceeds seven days, for whatever reason, the entire cycle must be restarted.

Crystalline Penicillin

Crystalline penicillin comes into play in more serious situations. Unlike benzathine, it is applied directly into the vein and acts much more quickly, which makes it indispensable when the bacterium has already compromised the central nervous system, a condition called neurosyphilis. In these cases, benzathine simply cannot penetrate the fluid surrounding the brain and spinal cord in sufficient quantity to eliminate the infection.

Treatment with crystalline penicillin is given in a hospital setting, every four hours, for ten to fourteen consecutive days.

In addition to neurosyphilis, crystalline penicillin is also indicated when treatment with benzathine did not produce the expected response, that is, when the VDRL titre does not fall as it should after complete treatment.

The Titre as a Guide to Cure

After treatment, the VDRL does not go to zero overnight, and this does not mean failure. What is expected is a progressive decrease in the titre over time:

  • At least two dilution points within six months for recent forms
  • Within twelve months for late forms

Someone who starts with 1:32 should be at maximum 1:8 within six months. If the titre remains steady or increases, retreatment is mandatory and immediate.

This is why, during pregnancy, the VDRL needs to be repeated every month. It is not an excess of testing, it is active monitoring of a disease that does not forgive those who wait.

Criteria for Baby Protection

It is worth reinforcing a point that many people do not know: treatment of the pregnant woman is only considered adequate to protect the baby if three conditions are met at the same time:

  1. The regimen must be correct for the stage of the disease
  2. Treatment must have been completed at least 30 days before delivery
  3. The partner also needs to have been treated

If any of these criteria fails, the newborn is automatically considered at risk and needs to be investigated, regardless of his or her own test results.

What Happens to the Newborn

In the baby, diagnosis is made with VDRL in umbilical cord blood or in a venous blood sample. When the baby's titre is higher than the mother's, this is a strong sign of active infection.

Depending on the clinical picture, the following may also be necessary:

  • Lumbar puncture to analyse the fluid around the brain
  • X-rays of the bones
  • Eye examination
  • Hearing assessment
  • Liver function tests

Treatment, when indicated, is done with crystalline penicillin for ten to fifteen days, in doses calculated by the baby's weight and gestational age, always within the hospital.

A Disease That Should Not Exist in 2026

Congenital syphilis is, above all else, a failure of the healthcare system. Not of an uninformed mother, not of a careless family: of the system. Because we are talking about a disease that is resolved with a cheap test and an antibiotic that has existed for decades, yet the figures remain alarming in Brazil, with tens of thousands of cases every year.

If you are pregnant or planning to become pregnant:

  • Do not put off the VDRL test
  • If the result comes back positive, treat without delay
  • If there is a partner in this situation, he needs to be treated at the same time, because a cycle is only broken when both sides of the chain are treated

Important notice: This text is exclusively informative and educational in nature, produced on the basis of scientific evidence and the protocols of the Brazilian Ministry of Health. It does not replace a medical consultation. Only a qualified healthcare professional can assess your case, request the appropriate tests and indicate the correct treatment. If you have any doubts or suspicions about your health or that of your baby, seek medical care immediately.