Twice-during-pregnancy STI screening reduces preterm birth risk by 23%, study finds

A randomized clinical trial published in Clinical Infectious Diseases found that screening and treating pregnant women for chlamydia, gonorrhea, and trichomoniasis twice during pregnancy reduces preterm birth risk by 23% compared to standard care. Conducted across four South African clinics with 2,247 participants by Penn and USC researchers, the study showed 80% of infections were asymptomatic. Single screening showed no birth risk reduction.

Effects of screening frequency on birth outcomes

• ▪In the Philani Ndiphile Study, screening pregnant participants for STIs only once at their initial prenatal visit resulted in an 18.9% preterm birth rate, failing to reduce risk.
• ▪Twice-pregnancy STI screening did not significantly reduce low birth weight alone or the combined primary outcome of preterm birth or low birth weight in the trial.
• ▪A Clinical Infectious Diseases trial found that screening and treating pregnant patients twice for three common STIs reduced preterm birth risk by 23% compared to standard care.
• ▪In the South African clinical trial, 14.5% of pregnant participants screened twice for STIs experienced preterm birth, compared to 18.8% receiving standard symptom-based care.

Co-lead author conclusions

• ▪According to co-lead author Andrew Medina-Marino, single-setting trial limitations mean further research is required to determine optimal STI screening timing and target patient populations during pregnancy.
• ▪Co-lead author Andrew Medina-Marino warned that relying solely on symptoms for STI treatment during pregnancy risks missing intervention opportunities, as most detected infections produce no symptoms.

Philani Ndiphile Study design

• ▪Researchers from the University of Pennsylvania and University of Southern California enrolled 2,247 pregnant participants across four South African clinics in a randomized trial evaluating routine STI screening.
• ▪The Philani Ndiphile Study tested pregnant participants for chlamydia, gonorrhea, and trichomoniasis either once at enrollment, twice during pregnancy, or upon symptom presentation.

STI prevalence among study participants

• ▪Among South African pregnant participants re-screened during their third trimester between 30 and 34 weeks of pregnancy, 9.2% tested positive for chlamydia, gonorrhea, or trichomoniasis.
• ▪In the Philani Ndiphile Study in South Africa, 27% of enrolled pregnant participants tested positive for an STI, and approximately 80% of infected participants showed no symptoms.