According to the Daily Mail, the popstar was with family in her hometown of Louisiana when her youngest son became unwell.
A source said: "One minute Britney and her sons were relaxing and enjoying their first visit to Kentwood in months, and the next minute Jayden had fallen ill.
"He was vague and unresponsive so Britney dialled an ambulance. But she was told it would take half an hour to arrive, and she was best trying to get Jayden to the hospital herself."
The two-year-old was taken to Southwest Mississippi Regional Medical Centre and "kept in hospital overnight for observations".
The source added: "We don't yet know what's wrong with him. Britney was insistent that she wouldn't leave him. She asked for a bed to be made up in the same room so she could be there at his side."