Almost all babies born to HIV mother can be free from the disease if appropriate steps are taken, research suggested today.

The biggest study to date into rates of transmission between mothers and babies found 99% of babies were born uninfected if recommended interventions were followed during pregnancy.

The infant infection rate was just 1.2% in the study - a huge drop on figures of around 20% in 1993.

Researchers said it was the first time such low rates of infection have been observed at a population level.

The study, published by Aids online, noted that most women now accept antenatal testing for HIV, which has had an effect on reducing transmission rates.

It said: "Uptake of antenatal HIV testing rose rapidly following the introduction of routine screening policies in 1999 in Ireland and between 2000 and 2003 in the UK, with the estimated proportion of infected women diagnosed before delivery increasing from about 70% in 2000 to about 95% since 2005."

Researchers also noted that most HIV positive women now take a combination of antiretroviral therapy (ART) drugs during pregnancy.

Data was analysed for 5,930 babies born to HIV mothers in the UK and Ireland between 2000 and 2006.

Transmission rates for women on ART for at least the last 14 days of pregnancy were 0.8%, regardless of type of therapy they received or whether they had a vaginal or caesarean birth.

Across the entire group of women known to have HIV, just 1.2% of babies were born with the disease.

"The low rate (1.2%) of MTCT (mother-to-child transmission) of HIV among diagnosed pregnant women in the UK and Ireland is a remarkable achievement," the authors said.

"Continuing to improve the offer and uptake of antenatal HIV testing could have a significant impact on further reducing MTCT, since most perinatally acquired infection is now in infants whose mothers are among the approximately 5% of infected women who remain undiagnosed at delivery.

"Ensuring that women are diagnosed in time to take up appropriate interventions remains a priority, and early testing for all pregnant women should continue to be promoted.

"Our findings suggest that offering HIV-infected women choices about HIV treatment and mode of delivery, according to current guidelines, has led to very low rates of MTCT."

Claire Townsend, research fellow at the University College London Institute of Child Health and lead author on the study, said: "Our findings are greatly encouraging.

"They demonstrate that if women are tested for HIV early enough in pregnancy for ART to be initiated, the risk of infection to their baby is very low indeed.

"This emphasises the importance of achieving and maintaining a high uptake of antenatal HIV testing on a national scale."

 The British Paediatric Surveillance Unit and the Royal College of Obstetricians and Gynaecologists also worked on the study, which was funded by the Health Protection Agency and the Medical Research Council.