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 i n Italy, we have considered data from a network of hospitals co-operating i n 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 s tatus 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 r ate was 9.7 per 100 children (this finding, however, was based on only six infected children and the trend was not statistically significant). Conside ring the overall series, the risk of vertical HIV transmission was higher i n women with low CD4 count in pregnancy [odds ratio (OR) <400 versus greate r than or equal to 400 1.8, 95% confidence interval (CI) 1.1-2.9], In compa rison 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 deliver y, In comparison with women who delivered at term (greater than or equal to 37 gestation weeks) the OR of HIV infection of the babies for the whole se ries was 2.2 (95% CI 1.3-3.6) in women who delivered preterm, Similar findi ngs emerged when the analysis was conducted considering, separately, subjec ts observed in the period 1988-1991 and 1992-1995, The frequency of Caesare an section increased from 26.5% of deliveries in 1988-1991 to 36.2% in 1992 -1995. Consequently, most temporal differences disappeared after standardiz ation for mode of delivery, but the rate in 1995 was still lower than in 19 88-1994.