Objectives: To identify risk factors for vertical HIV transmission that may provide opportunities for the prevention of future pediatric HIV infection.

Study design: A prospective cohort of 44 pregnant HIV(+) women and their 53 offspring was followed between July 1989 and July 1996.

Results: Secondary and latent maternal syphilis infection was diagnosed in four pregnancies with VDRL titers > or = 1:128. Concurrent maternal syphilis infection was associated with 100% vertical HIV transmission (4/4), compared to 21% (3/14) deliveries that occurred in 13 women with only a history of treated sypillis (P = 0.01) and 14% (5/35) deliveries in women with no history of syphilis (P = 0.0015). Among non-Zidovudine exposed pregnancies, 100% (3/3) patients with concurrent syphilis transmitted HIV to their infants vs. 0% (0/8) patients with only a history of syphilis (P = 0.006). A history of treated syphilis did not increase subsequent transmission risk compared to women with no history of syphilis (3/14 vs. 5/35, P = 0.41). One patient delivered twice during the study and received Zidovudine prophylaxis during both pregnancies. Her first pregnancy VDRL titer was > or = 1:128, during which she delivered an HIV infected child. Following successful treatment for syphilis (VDRL titer, 1:1), she conceived again and delivered an uninfected infant 11 months later. Additional risk factors significantly associated with vertical HIV transmission were prematurity and low birth weight. Variables studied but not statistically-related to HIV transmission included: other sexually transmitted diseases, maternal age, race, intravenous drug or cocaine use, prenatal care, route of delivery, duration of HIV(+) status, and CD4 count.

Conclusion: Among HIV(+) women, concurrent syphilis infection, but not a history of syphilis, is significantly associated with vertical perinatal HIV transmission. Frequent screening and prompt treatment of syphilis in non-pregnant HIV(+) women may help prevent subsequent HIV infected pregnancies.