Khadija Khan was held against her will and was forced to take part in the kidnapping of baby Revelation Jones, the Johannesburg Magistrate's Court heard on Friday.
The claim was contained in an affidavit by Khan, which was read into the record by magistrate PJ du Plessis.
"My boyfriend kidnapped the baby and assaulted the nanny. He kept the baby in a hotel for two days... I was also held against my will in the hotel," she said in the document.
"I pleaded with him to return the baby."
Khan is reportedly seven months pregnant. She has three other children from a previous marriage.
She and her boyfriend Khalid Ayub were applying for bail.
They allegedly kidnapped the baby from his parents' house in Bezuidenhout Valley on January 8 and tried to slit his nanny's throat.
The infant's father received an sms to pay R100 000 in exchange for the baby's safe return.
The couple, who had rented a room in the family's house, was arrested in Fordsburg on January 10 after a tip-off. The baby was found unharmed.
They also face a charge of robbery with aggravating circumstances.
In his affidavit, Ayub said he needed to be home to take care of his as yet unborn baby with Khan.
However, Du Plessis said this was not a satisfactory reason to grant bail.
"He is not the one expecting the baby. His partner is," he said.
The hearing continues.