STI screening should be performed for at-risk pregnant women at the initial prenatal visit. Which test does not require retesting during the third trimester?

In the context of STI screening for at-risk pregnant women, it is important to understand the guidelines for each test. The rubella titer is a blood test that determines immunity to rubella, also known as German measles. If a woman is found to be immune to rubella at the initial prenatal visit, no further testing is necessary during the third trimester, as her immune status will not change.

In contrast, screenings for chlamydia, syphilis, and HIV are typically recommended to be repeated during the third trimester for at-risk pregnant women. This is due to the potential for new infections or changes in status that can occur during the pregnancy. For instance, chlamydia can be asymptomatic and may not show up in initial screenings, while syphilis and HIV can also be contracted after the initial test.

Therefore, the rubella titer stands out as the only test listed that does not require retesting during the third trimester, as it assesses immunity rather than current infection status.