In a June 2025 Science Speaks blog post, I wrote about the unacceptably low rates of screening for hepatitis C virus in pregnancy. I see a lot of young women with HCV who have been pregnant and are shocked that they weren’t screened by their obstetrician. Since 2020, the Centers for Disease Control and Prevention, followed by multiple medical societies, has recommended that pregnant people be screened for HCV with each pregnancy, but we are screening less than 40% of them.
In an new study published in Open Forum Infectious Diseases, researchers looked at all pregnant women who tested positive for syphilis in West Virginia between Jan. 1, 2019, and Dec. 31, 2023. They interviewed all women with a positive syphilis test to collect other information: age, race, syphilis diagnosis and treatment, past-year incarceration, past-year substance use and birth outcomes. Both syphilis and HCV are reportable conditions, so they cross-referenced those records.
They found 161 pregnancies with a positive syphilis test; 69 (42.9%) had laboratory evidence of a past or present HCV infection. Of these, 38 (55.1%) had active HCV during this pregnancy. While approximately one-third of all patients had an unknown incarceration or drug use history, 21.7% of women with HCV were incarcerated in the last year versus 5.4% who did not have HCV. In addition, 50.7% of the patients with HCV reported drug use in the prior year versus 15.2% who did not have HCV.
Discrepances were also seen with syphilis treatment adherence, with those with HCV being more nonadherent to treatment (40.6% vs. 14.1%). Unsurprisingly, the group with HCV also had higher rates of congenital syphilis (59.4% vs. 28.3%).
This association between syphilis and HCV is somewhat surprising. HCV is not considered a sexually transmitted disease with heterosexual spread. The authors of the OFID study highlighted higher rates of substance use and incarceration in the co-infection group. Not only does this study reinforce the need for universal testing for both syphilis and HCV in pregnant people, but it is a call to clinicians to ensure close follow-up during syphilis treatment for those who are positive for both syphilis and HCV.
Further studies could look at whether linking patients with substance use disorder into treatment would improve syphilis treatment adherence and reduce the rates of congenital syphilis.
This study starts to uncover the syndemics of infectious diseases in pregnancy and may provide a glimpse into how to improve health care for pregnant and postpartum patients and their families.