The use of back-projection to estimate HIV prevalence in preganant women

Objective: To estimate the number of children infected with HIV perinatally, and the prevalence of HIV infection in pregnant women.

Methods: A statistical method similar to back-projection was used to estimate the number of children infected with HIV perinatally from the number of children with AIDS due to perinatal HIV infection and knowledge of the rate of progression from HIV infection to AIDS.

Results: By 31 December 1994 there were 20 children in Australia reported to have AIDS due to perinatal HIV infection. Based on these 20 AIDS cases, it was estimated that to the end of 1994 there were between 48 and 84 children in Australia infected with HIV perinatally. Assuming that the transmission rate of HIV from infected mothers to their babies was 25%, it was estimated that the prevalence of HIV infection among women giving birth in Australia had increased from 0.03 per 1000 in 1983-1985 to between 0.09 and 0.20 per 1000 in 1992-1994.

Conclusion: This range for the prevalence of HIV infection among pregnant women in 1992-1994 was consistent with estimates of the prevalence from screening studies, and suggests that the prevalence of HIV infection in pregnant women in Australia has increased but remains low.