Introduction 

Congenital syphilis occurs when a mother who has syphilis passes it on to her foetus via the bloodstream. Syphilis is a sexually transmitted infection (STI) and can result in a number of serious consequences for the baby, including stillbirth and neonatal death ( death soon after a live birth). If the mother has untreated syphilis before she becomes pregnant, it can be passed onto the foetus. It can also be passed on if she acquires the infection during pregnancy. 

What is syphilis?

Syphilis is caused by the bacterium Treponema pallidum. Syphilis can be transmitted by vaginal, anal or oral sex. It can affect both people assigned male (AMAB) and female at birth (AFAB). Syphilis can be diagnosed either by a rapid lateral flow test or by a blood test – the latter can show the result within a few minutes.⁵

Global spread of syphilis

Syphilis is one of the most common STIs with approximately 6 million new cases every year. It occurs more commonly in low and middle-income countries. There are many low and low to middle-income countries where it is endemic. In middle and high-income countries, even though rates went down during the 1990s, many countries in Europe and China have seen increases in syphilis in recent years, partly due to funding cuts in sexual health services. It is most prevalent in people AMAB who have sex with other people AMAB. However, this does not mean to say that other people are not at risk – those in heterosexual relationships can also have syphilis. AFAB sex workers and their male clients are amongst the most high-risk groups in society.¹ In the US, congenital syphilis cases are going up in several states, disproportionately affecting those of ethnic minorities.⁴ 

Globally, congenital syphilis cases have been between 700,000 and 1.5 million every year between 2016 and 2023. 62% of which have been in African countries.⁵ 

Stages of syphilis

The disease has four stages – primary, secondary, latent and tertiary. The main symptom of primary syphilis is an ulcerated lesion called a chancre which appears on the genitals in most cases, although they can appear elsewhere too. It is usually painless, and without treatment will disappear within 6 weeks. Those with a chancre may not always be aware of it as it is painless and may be in a location that is difficult (or not possible) to see such as the anus, under the foreskin or in the cervix. Even if the chancre resolves by itself, it is important to receive treatment to prevent further progress of the infection. 

Secondary syphilis, in 50% of cases involves a rash on the palms of hands and soles of feet. There can also be rashes around the genital area known as condyloma lata. Other symptoms can include enlarged lymph glands, feeling generally unwell, and body aches. 

After the secondary stage, there is a stage known as the latent stage where the patient does not experience any symptoms. The latent stage can last for many years, and although there are no symptoms, the damage is still being done, and if left untreated will progress. 

The final stage is the tertiary stage where there is damage to multiple internal organs and the nervous system resulting in a range of serious health issues. This can happen years even up to decades after the initial infection. At this stage, syphilis can be fatal.^1,5

Diagnosis

Diagnosing syphilis can be difficult. Syphilis has in the past been referred to as ‘the great imitator’ or ‘the great masquerader’ as it can mimic other conditions, especially in the secondary stage. The symptoms can vary from person to person, and it can be difficult to identify the initial point of infection. However with modern blood tests and lateral flow tests, diagnosis is much easier.6 Syphilis testing is not done for all pregnant individuals in every part of the world, it is mostly done for women in some endemic countries. In other cases, it may be up to the person themselves to have a sexual health check.⁵

Congenital syphilis 

It is during the primary and secondary stages of syphilis that the bacteria are most likely to transmit from the mother to the foetus, as the bacteria are in their highest concentration in the blood. There is still a risk of the disease being passed on in the latent or tertiary stages but this is lower than the previous two stages, although it can result in adverse effects.

As mentioned earlier, the consequences of congenital syphilis can be severe, especially if the mother has syphilis in the second or third trimester. Around 70% of untreated primary and secondary syphilis results in some effect on the foetus, with a 26% chance of stillbirth.² According to WHO figures, in 2016, there were 661,000 total congenital syphilis cases globally. Of these, there were:

• 143,000 early foetal deaths and stillbirths (death of the foetus after 20 weeks of pregnancy)
• 61,000 neonatal deaths 
• 41,000 preterm or low-birth-weight births

Some babies with syphilis do not show any symptoms at birth. However, they usually appear within three months of birth. These can involve symptoms affecting the liver, such as abnormal blood test results, jaundice, and an enlarged liver. Babies can be born with a rash all over their body. They can have rhinitis (inflammation around the nasal passages), with a white-coloured discharge. This usually happens within a week or so of birth. Their lymph nodes may also be enlarged. This is also known as ‘early congenital syphilis’. 

If it is undetected around the time of birth (and therefore not treated), usually in the case where there are no symptoms earlier in life, older children can also present with syphilis symptoms. These can include abnormalities in the bones and teeth, intellectual disabilities, and abnormalities in facial structure. They may also have problems with hearing and vision. This is also known as ‘late congenital syphilis’. By this time, the symptoms will not be treatable but can be managed. They will persist into adulthood.^1,2,3

Treatment of syphilis 

Treatment for pregnant individuals who have early-stage syphilis is a single dose of long-acting penicillin, usually by injection. According to research, this is 98% effective, especially if they receive treatment before the second trimester. This is usually enough to leave only a minimal impact on the foetus. Later stages of syphilis are also treated by penicillin but with more doses over a longer period of time. 

Treatment for babies born with syphilis is by penicillin given intravenously (on a drip) to the baby. Doses and length of treatment depend on the age of the baby when they are diagnosed and their weight. 

Prevention of syphilis 

Practicing safe sex, for example by using condoms, and getting tested regularly (especially in the case of multiple sexual partners) is important for reducing the risk of STIs.² It should be noted that contraceptive pills or implants do not help in preventing STIs. Those who are diagnosed should inform their sexual partners.²

Testing and treatment are the most effective ways of managing syphilis. Early intervention is essential for reducing risks to both mother and baby. Babies who are born with signs of syphilis, or born to a mother who has had untreated syphilis should have treatment straight away to prevent serious adverse health outcomes.⁵ 

Testing 

Testing for neonates is not done routinely for all babies, but if the mother has had a positive test, then the baby will also be tested. 

It is important for pregnant individuals to be tested for syphilis, and for them to attend prenatal appointments and tests. If a positive test for syphilis is found, it should be treated promptly. It may not always be obvious if a sexual partner has syphilis, so it is important to remain vigilant. Having syphilis increases the risk of acquiring other STIs including genital herpes, chlamydia, and gonorrhoea. The chance of getting HIV is almost doubled if someone already has syphilis.⁵ 

Healthcare providers play an important role in treating and following up with those who are pregnant and have syphilis.⁴ 

Summary 

Congenital syphilis occurs when a pregnant individual who has syphilis passes it on to the foetus in utero. Syphilis can be acquired by the mother before or during pregnancy. For the foetus, syphilis can result in a number of adverse outcomes including stillbirth or neonatal death. Not all babies who are born with syphilis will have symptoms at the time of birth. Some will develop symptoms a few weeks or months after birth, and others not until later on in childhood- at which point the symptoms can be persistent. 

It is important to practise safe sex and to be tested regularly, especially for those who have multiple sexual partners. Prompt treatment with penicillin has high success rates and will prevent adverse health outcomes for the mother and baby. However it should be noted that an increased use of antibiotics such as penicillin can lead to antibiotic resistance, hence they should be used only when necessary.