Mother-to-child transmission of human immunodeficiency virus in Italy : temporal trends and determinants of infection

In order to analyse temporal trends in vertical transmission rates of human immunodeficiency virus (HIV) and determinant of congenital HIV infection in Italy, we have considered data from a network of hospitals co-operating in the Italian Collaborative Study on HIV infection in pregnancy, conducted between 1988 and 1995. A total of 1040 women entered the study. The HIV-1 status of the babies was known in 848 cases (81.5%). Transmission rates were highest in the period 1988–1991, then tended to decrease and in 1995 the rate was 9.7 per 100 children (this finding, however, was based on only six infected children and the trend was not statistically significant). Considering the overall series, the risk of vertical HIV transmission was higher in women with low CD4 count in pregnancy [odds ratio (OR) <400 versus ⩾400 1.8, 95% confidence interval (CI) 1.1–2.9]. In comparison with vaginal delivery the risk of transmission was 0.3 (95% CI 0.1–0.5) and 0.6 (95% CI 0.3–1.2) respectively for elective and emergency delivery. In comparison with women who delivered at term (⩾37 gestation weeks) the OR of HIV infection of the babies for the whole series was 2.2 (95% CI 1.3–3.6) in women who delivered preterm. Similar findings emerged when the analysis was conducted considering, separately, subjects observed in the period 1988–1991 and 1992–1995. The frequency of Caesarean section increased from 26.5% of deliveries in 1988–1991 to 36.2% in 1992–1995. Consequently, most temporal differences disappeared after standardization for mode of delivery, but the rate in 1995 was still lower than in 1988–1994.