Cuba has become the first country in the world to eliminate the transmission of HIV and syphilis from mother to baby, the WHO said, hailing the success as "one of the greatest public health achievements possible."
"This is a major victory in our long fight against HIV and sexually transmitted infections, and an important step towards having an AIDS-free generation," said Dr Margaret Chan, World Health Organisation (WHO) Director-General.
"Eliminating transmission of a virus is one of the greatest public health achievements possible," she said.
"This is a celebration for Cuba and a celebration for children and families everywhere. It shows that ending the AIDS epidemic is possible and we expect Cuba to be the first of many countries coming forward to seek validation that they have ended their epidemics among children," said Michel Sidibe, Executive Director of UNAIDS.
Every year, globally, an estimated 1.4 million women living with HIV become pregnant. Untreated, they have a 15-45 per cent chance of transmitting the virus to their children during pregnancy, labour, delivery or breastfeeding.
However, that risk drops to just over 1 per cent if antiretroviral medicines are given to both mothers and children throughout the stages when infection can occur.
The number of children born annually with HIV has almost halved since 2009 - down from 400,000 in 2009 to 240,000 in 2013, WHO said.
But intensified, efforts will be required to reach the global target of less than 40,000 new child infections per year by 2015, it said.
Nearly one million pregnant women worldwide are infected with syphilis annually. This can result in early foetal loss and stillbirth, neonatal death, low-birth-weight infants and serious neonatal infections.
However, simple, cost-effective screening and treatment options during pregnancy, such as penicillin, can eliminate most of these complications, according to WHO.
WHO and Pan American Health Organisation (PAHO) have been working with partners in Cuba and other countries in the Americas since 2010 to implement a regional initiative to eliminate mother-to-child transmission of HIV and syphilis.
As part of the initiative, the country has worked to ensure early access to prenatal care, HIV and syphilis testing for both pregnant women and their partners, treatment for women who test positive and their babies, cesarean deliveries and substitution of breastfeeding.
Among the 22 countries which account for 90 per cent of new HIV infections, 8 have already reduced new HIV infections among children by over 50 per cent since 2009, based on 2013 data, and another four are close to this mark, WHO said.
As treatment for prevention of mother-to-child transmission is not 100 per cent effective, elimination of transmission is defined as a reduction of transmission to such a low level that it no longer constitutes a public health problem, it said.
