Gauteng – A pair of three-week old conjoined twins were on Saturday successfully separated during a six-hour operation at Netcare Unitas Hospital in Centurion.The girls, Uwenzile and Uyihlelile Shilongonyane from Swaziland, had a combined weight of 4.21kg when they were born by C-section on January 2.The babies were joined at the lower abdomen and each had their own heart and other vital organs, improving their chances of surviving the separation, paediatric surgeons Dr Mariza de Villiers and Dr Paul Stevens said ahead of the operation.The twins were the second set the surgeons have separated.The hospital explained in a statement that the twins were joined only by a bridge of skin, simplifying the operation."The fact that there was a skin bridge between them meant that there was sufficient skin to close the resultant surgical wound on each baby without the need for plastic surgery," De Villiers said.Anaesthesia was the main challenge facing the surgical team, Stevens said.Second set of twins"The twins were conjoined in such a way that they are facing each other. Intubation for such tiny babies is delicate enough, but as their faces are so close to one another and they are not able to be placed on their backs to be intubated for anaesthesia, this was a great deal more complicated than usual."Four anaesthetists, wearing colour-coded scrub caps, took care of the twins during the surgery.Getting the anaesthetic "just right" for the surgery, took more than three hours, almost half of the total theatre time.The twins were officially separated at midday and the surgery was completed shortly before 14:00.(Supplied)The twins' parents, Bongkile and Mbongeni, found out they were expecting a second set of twins when Bongkile was seven-months pregnant.Their first set, both boys, are two."At first I was not happy to hear that I was expecting twins for the second time," she said. "However, once they were born everything changed. After their birth I was at first not worried as I thought the babies were only attached at the umbilical cord."The hospital’s general manager Robert Jordaan said they were impressed by the ease with which Bongkile handled her conjoined babies, "considering the difficulty in doing something as basic as picking them up".Eight doctors and a theatre team of 11 nursing professionals took part in the procedure.