517   Perinatal Transmission of HIV-1 from Pregnant Women with RNA Viral Load Less than 1000 Copies/ml.

J. J. Goedert, L. Gray, B. T. Korber, M. J. Mayaux, L. M. Mofenson, M.-L. Newell, D. E. Shapiro, J. P. Teglas, and C. M. Wilfert.
Univ. of Ioannina Sch. of Med., Greece; Columbia Univ. Coll. of Physicians and Surgeons, New York, NY; Global Strategies for HIV Prevention, San Rafael, CA; CDC, Atlanta, GA; VEB/DCEG/NCI, NIH, Rockville, MD; Inst. of Child Hlth., London, UK; Santa Fe Inst., NM; INSERM Unite 292, Le Kremlin Bicetre, France; NICHD, NIH, Rockville, MD; CBAR, Harvard Sch. of Publ. Hlth., Boston, MA; and Duke Univ. Med. Ctr., Durham, NC.

Background:Perinatal transmission of HIV-1 has been reported to occur occasionally even among women with very low HIV-1 RNA levels. We evaluated how frequent transmission is, when the maternal RNA is <1000 copies/ml, and whether antiretroviral therapy or other parameters may affect the risk of transmission among these women.

Methods:We conducted a meta-analysis that combined individual patient data from 7 European and U.S. prospective studies of maternal infant-transmission. Data were collected on several potential predictors of transmission for mother-infant pairs where the maternal viral load at or closest to delivery was <1000 copies/ml.

Results:A total of 44 cases of vertical HIV-1 transmission were identified among 1,202 women with HIV-1 RNA <1000 copies/ml at or close to delivery. The transmission rate was only 8/834 (1.0%; 95% confidence interval [CI], 0.4—1.9%) for mothers receiving antiretroviral treatment during pregnancy and/or delivery vs. 36/ 368 (9.8%; 95% CI, 7.0—13.4%) for untreated mothers (risk ratio 0.10; 95% CI, 0.05—0.21). In multivariate analysis adjusting for study, transmission was lower with antiretroviral treatment (odds ratio [OR] 0.10, P < 0.001), cesarean section (OR 0.30, P = 0.022), greater birth weight (P = 0.003) and higher CD4 cell count (P = 0.039). In 12/44 cases, multiple RNA measurements were obtained during pregnancy, delivery or within 4 months postpartum; in 10/12 cases, the geometric mean was <500 copies/ml.

Conclusions:Perinatal transmission occurs in only 1% of treated women with RNA <1000 copies/ml and may be almost eliminated with antiretroviral prophylaxis accompanied by suppression of maternal viremia.