Data on 5,151 HIV pregnancies in the UK and Ireland between 2000 and 2006 found 99% of babies were born uninfected if recommended steps were taken to prevent the disease being transmitted.
In the mid-1990s, before effective drug therapy became available, the infant infection rate was over 20%.
More women took antenatal tests for HIV and most pregnant women with the disease took a combination of antiretroviral therapy drugs.
“Our findings are greatly encouraging,” said researcher Claire Townsend, from the University College London Institute of Child Health.
Lisa Power, of the HIV charity Terrence Higgins Trust, said: “With the right treatment and relevant support, the vast majority of women living with HIV can have healthy uninfected children.
“This is why testing for HIV in pregnancy is so important and why treatment for pregnant women living with HIV in the UK should always be free, whatever their immigration status.”