Co-authored by WHO and HRP with partners, and published in the scientific journal PLOS ONE, the new estimates show that out of the 661,000 total cases of congenital syphilis, there were 355,000 adverse birth outcomes – which represents a significant proportion of newborn death and disease.

The estimates showed that the overall global burden of congenital syphilis decreased over the 2012 to 2016 research period, although non-significantly, from around 750,000 to 660,000 cases. The research also found some improvements in screening, treatment, and surveillance of maternal syphilis. Estimated adverse birth outcomes due to congenital syphilis decreased slightly from 397,000 to 355,000.

Syphilis is one of the most common sexually transmitted infections globally, with approximately 6 million new cases each year. If a pregnant woman who is infected does not receive early and effective treatment, she can then transmit the infection to her unborn infant. This is known as ‘congenital syphilis’, which is often fatal. It can also cause low birth weight, prematurity, and other congenital deformities. Congenital syphilis is the second leading cause of preventable stillbirth globally, preceded only by malaria.

Congenital syphilis is easily preventable and treatable – as long as testing and treatment are provided to pregnant women early during antenatal care. The risk of adverse outcomes to the fetus is minimal if a pregnant woman, infected with syphilis, receives testing and adequate treatment with benzathine penicillin, early in pregnancy – ideally before the second trimester.

Despite the decrease between 2012 and 2016, the numbers of affected women and infants remains unacceptably high. It is crucial that all women are provided with early syphilis screening and treatment as part of high-quality antenatal care for a positive experience of pregnancy.

In addition, health systems and programmes need to ensure that all women diagnosed with syphilis, as well as their infants, are effectively treated – and that their sexual partners are reached for testing and treatment. Countries can also work to reduce syphilis prevalence across populations, by ensuring that testing, treatment and partner referral for the infection are put into action, beyond that of antenatal care.