Twice STI Screening Cuts Preterm Birth Risk
A South African clinical trial found that testing pregnant women for sexually transmitted infections twice during pregnancy was linked to a lower rate of preterm birth.
Updated on Nov. 4, 2026 in Pregnancy
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Would you ask your doctor for STI screening during a future pregnancy even without symptoms?
A clinical trial of more than 2,200 pregnant women at four government health clinics in South Africa found that screening for chlamydia, gonorrhea and trichomoniasis twice during pregnancy reduced the risk of preterm birth by 23%. Screening only once was not associated with lower odds of preterm birth.
Why it matters
Many STIs cause no symptoms, so routine testing may catch infections that standard symptom-based care misses. The findings add evidence on prenatal screening at a time when researchers are still determining how often pregnant patients should be tested.
About 27% of women screened at the start of the study tested positive for at least one of the three STIs, and about 80% of those infected showed no signs or symptoms. Only about 9% of women rescreened in the third trimester tested positive, and the study did not find a significant reduction in low birthweight.
The players
University of Pennsylvania
A private Ivy League research university in Philadelphia whose researchers led the trial and which published the news release on the findings.
The details
Women were randomly assigned to single screening, double screening, or standard symptom-based care. Those in the double-screening group were tested at their first prenatal visit and again between 30 and 34 weeks of pregnancy, with treatment and follow-up for those who tested positive.
Timeline
Oct. 29, 2026: University of Pennsylvania published a news release on the trial.
Nov. 4, 2026: HealthDay reported the trial findings.
Between 30 and 34 weeks of pregnancy: second screening window for the double-screening group.
Health Landscape
The trial tests routine screening against the symptom-based prenatal care that has long been the standard comparator in studies of pregnancy infections. Its finding that a second screening reduced preterm birth, while a single screening did not, adds to the evidence base that health systems weigh when setting prenatal testing protocols.
Pregnant women may ask their prenatal providers whether repeated STI testing during pregnancy is recommended for them, since many infections cause no symptoms. Testing and treatment decisions remain a conversation with a healthcare provider.
The takeaway
Many sexually transmitted infections in pregnancy produce no symptoms, so routine testing can matter even when a woman feels well. Patients should discuss prenatal screening schedules with their healthcare provider.
Further reading
For more on prenatal care and pregnancy health, explore our Pregnancy section.
Live Poll
Would you ask your doctor for STI screening during a future pregnancy even without symptoms?
