And healthcare costs for these children are increasing. Dr Anban Pillay, director of health financing and economics in the Department of Health, said: "The cost of [preventing mother-to-child transmission of HIV] is far lower than lifetime treatment on antiretrovirals. It's a no-brainer."
On Tuesday, Health Minister Aaron Motsoaledi appeared relieved that the province with the highest HIV prevalence rate, KwaZulu-Natal (39.5%) had one of the lowest mother-to-child HIV transmission rates in the country, at 2.9%.
A Medical Research Council study presented at the national Aids conference in June showed that the national mother-to-child HIV transmission rate was 3.5%. In 2008, the figure was 8.8%.
Motsoaledi said South Africa was "doing very well" because "we were able to cut [the rate] in half" in two years. But the Medical Research Council study showed an almost threefold difference in preventing mother-to-child transmission across the provinces:
Gauteng: 2.5%;
KwaZulu-Natal: 2.9%;
Limpopo: 3.6%;
Western Cape: 3.9%;
North West: 4.4%;
Mpumalanga: 5.7%; and
Free State: 5.9%.
Sample sizes in Northern Cape and Eastern Cape were insufficient to give an accurate reflection of the rate of HIV transmission.
Lead researcher Ameena Goga said the national average transmission rate of 3.5% was based on HIV tests on babies up to eight weeks old. But if the study had been of 18-month-old babies the transmission rate would have been "likely to exceed 5%" because of mixed feeding practices and shortages of prophylactic drugs.
In September, the executive director of UNAids, Michel Sidibé, travelled to South Africa after the launch of the global plan "Countdown to zero". The plan is intended to eliminate HIV infection of children worldwide by 2015.
Sidibé recalled elders in his Malawian village saying: "If you want to kill the snake, you have to be able to hit the head of the snake. He said: "The head of the epidemic in this region is South Africa. You cannot win the battle against HIV/Aids if you fail in South Africa."
UNAids estimated that 42726 South African babies contracted HIV from their mothers in 2010. This is almost double the figure in other sub-Saharan African countries, such as Mozambique (26491), Uganda (24548) and Kenya (21869). South Africa also has the most children under the age of 14 living with HIV in the world - 333941.
In a ranked comparison, this figure towers above the next country on the list, Mozambique, which has 127677 HIV-positive children under the age of 14. UNAids reports that more than 29000 South African children under 14 die from Aids every year.
Said Sidibé: "It will cost us $100 to stop transmission from the mother to the baby. But if a baby is born with HIV it will cost us $150000 for treatment only. So [preventing mother-to-child-transmission] is value for money. It is a political opportunity and is about saving life - and it's possible."