Of all US mothers who had given birth between January 2016 and December 2019, 1.9% (267,260) had chlamydia, 0.3% had gonorrhea and 0.1% were infected with syphilis before or during their pregnancies. Among all newborns, 8% (1,146,800) were born prematurely. Mothers with chlamydia, gonorrhea or syphilis were 1.04, 1.10 and 1.17 times more likely to have a moderately preterm birth — meaning between 32 and 36 weeks of gestation — than women without STIs, respectively, the authors found.
Infections with gonorrhea and syphilis were more strongly associated with very preterm births, which meant between 28 and 31 weeks.
“Even though some of the effects are small, STIs do appear to increase your chance of delivering preterm,” said Kelli Ryckman, a coauthor of the study and a professor of epidemiology at the University of Iowa’s College of Public Health.
How STIs could affect birth time
“All of these responses may cause inflammation and activate the maternal and/or fetal immune system, which is an established cause of preterm birth,” the researchers suggested. “However, whether a maternal infection induces preterm birth may also depend on the characteristic and concentration of the pathogen and the timing of infection.”
Observational studies such as this one can’t take into account individual behaviors and other factors potentially responsible for preterm birth, including chronic stress, gestational age of diagnosis or lack of access to treatment, Adhikari and Roberts wrote.
“Without a better understanding of which infections were and were not treated, we have little to guide a search for targeted interventions to prevent preterm birth in a cohort with treatable infectious diseases,” they added.
For women, symptoms of chlamydia, gonorrhea and syphilis don’t always appear given the sometimes silent nature of early stages of infection. But symptoms can include abnormal vaginal discharge or bleeding; burning sensation while peeing; rectal pain, discharge, itching or bleeding; or painful bowel movements. Early signs of syphilis are sores that can be firm, round and painless.
If you’re pregnant and “suspect you could have an STI, consult with your primary care physician or obstetrician and get tested and then treated if you are infected,” Ryckman said. “If you are infected with an STI, make sure to discuss your risks for pregnancy complications with your obstetrician.”
Below are the CDC’s resources for more information and clinic referrals: