The mother of a newborn baby kidnapped from her hospital bedside 18 years ago broke down and wept in a South African court on Tuesday as she described how she awoke to find the girl had vanished.

Celeste Nurse, 36, gave evidence in the Cape Town High Court in a case of astonishing coincidence which saw her finally reunited with her daughter only last year.

Standing in the witness box just metres from the 50-year-old woman accused of kidnapping her baby, Nurse kept her composure before bursting into tears when she was asked what she had named the girl.

"Zephany Joy Nurse," she replied.

The accused woman, who pleaded not guilty to kidnapping, cannot be named as this would reveal the stolen girl's new identity.

The kidnapped girl, who is now 18, asked for court protection from the media storm which greeted her discovery in February last year.

That came about when a younger daughter of the Nurse's, Cassidy, began attending high school and pupils pointed out her remarkable likeness to a final year student.

The younger girl told her parents, who met the older girl and immediately believed she was their long-lost baby.

Her parents called the police, and DNA tests confirmed that the girl was indeed Zephany.

In court, Celeste Nurse, in a checked skirt and black T-shirt, described how Zephany had been stolen at Cape Town's Groote Schuur hospital on March 30, 1997, when she was just three days old.

Nurse said she was sleeping under medication in a bed closest to the ward door, with her baby in a cot next to the door, when she woke groggily to hear the girl crying.

"I saw a person sitting at the door" dressed as a nurse, she said.

"She asked me 'can I pick up the child?' I said yes. That's all I can remember until a nurse woke me and asked where the baby was.

"I asked 'what do you mean, the nurse was just here with the baby'.

"We ran everywhere in the hospital. The baby was nowhere to be found. Missing. Gone."

The accused woman, dressed in slacks and a striped top, listened intently at times and at others gazed down into her lap.

Without knowing it, the Nurse family had been living within a couple of kilometres (miles) of their kidnapped daughter, celebrating her birthday every year and never giving up hope of finding her.

Zephany is now approaching her 19th birthday after reportedly being raised with love and kindness by the accused woman and her husband, who she believed were her real parents.