Background:  The current standard of care for pregnant women in the United States includes universal HIV antibody testing early in pregnancy, typically in the first trimester. After this time, women are typically considered HIV^­ and thus, low risk with no further testing offered. However, this practice does not consider women who are acutely infected or become infected later in pregnancy. We report on North Carolina’s statewide use of an enhanced HIV testing strategy to detect both acute and established HIV infection at prenatal HIV testing and its effect on perinatal transmission.

Methods:  Since 2002, North Carolina’s Screening & Tracing Active Transmission (STAT) program for HIV voluntary counseling and testing has retested all antibody EIA^­ specimens for HIV RNA following specimen pooling; patients with EIA^­ HIV RNA⁺ results are immediately traced for clinical evaluation, confirmatory testing and partner counseling and referral services.

Results:  From November 1, 2002 through June 1, 2005, 202,114 North Carolina women at risk for HIV received public HIV testing, of whom 50,766 (25%) were tested in prenatal and obstetric clinics. Among all women, 475 (0.2%) were HIV infected. Antibody tests were positive in 459 (96.6%) cases but were negative in 16 (3.4%) RNA⁺, acutely infected women. Of these 16 acute cases, 5 (31%) were in fact pregnant at testing. Of 45 (4.4%) new infections detected, 2 were tested in prenatal and obstetric testing sites. All pregnant, acutely HIV-infected women were located, counseled, and initiated on ART. To date, 4 of 5 infants have been delivered, and none of 4 evaluable infants have been HIV infected. During this same period, at least 2 infants were born HIV infected in North Carolina whose mothers were found to have been HIV-antibody negative early in pregnancy.

Conclusions:  Standard antibody tests miss at least 4% of the pregnant women in North Carolina who are infected with HIV; testing algorithms including pooling/RNA significantly improve performance. Despite high viremia in the mother, ART initiated early in acute HIV infection can be effective in preventing transmission to infants. Strategies to reduce residual perinatal transmission of HIV in the United States must address the risk of maternal infection during pregnancy.